Common Sense Rules for Magical Items
Everyone dreams of playing legos with spells to make cool magical items. It is largely up to the DM to set limits on that, which can be a source of frustration on both sides of the screen as D&D's rules are burdensome to a campaign and lack core principles to work from.
With these optional rules you don't have to argue. Derived from D&D's baked-in principles of affinity, capacity, permanence, and complexity you can easily plan and create magical items and effects, with minimal disruption to the campaign and realistic costs.
Once you understand these really simple concepts, the only limit is your imagination. Also, the last section has useful examples to work from.
1. Affinity
Magic wants to leave spellcasters and do its thing. Trying to get it to stay in an object is hard. Affinity is how strong an object attracts magic. Spellcasters have high arcane affinity, which is why they are able to recharge spell slots. When an object attains a high enough affinity, it will draw its own arcane power and recharge on a long rest as spellcasters do.
Affinity in magical objects primarily comes fromn time and proximity to magic being used, like iron becoming magnetized by being close to another magnet.
Gathering affinity
If a spellcaster focuses on an object in their possession while casting a 1st level spell, it gains 1 point of affinity. If a caster does the same for an object with a 9th level spell, the object gains 9 points of affinity. Affinity increases the longer concentration on a spell is held.
| Concentration Duration | Total affinity gained |
|---|---|
| 1 round/reaction | 1 x spell level |
| 1 minute | 2 x spell level |
| 10 minute | 3 x spell level |
| 1 hour | 4 x spell level |
So, the reason it takes time to create a spell scroll is that you have to create enough affinity in the scroll or object for it to retain the magic required by the spell.
Self-charging
If an object has magical affinity, it will gather arcane power gradually until it reaches its maximum capacity. Affinity determines how much power collects per day.
- Charges per day = (affinity/100) / spell level
3rd level caster example
Consider a 3rd level wizard who casts their full spell complement daily, with 1 minute concentration on one out every four spells they cast.
This wizard will generate 10 affinity points per day.
To create a magical artifact that generates one level one spell charge per day would require 100 pts. So this would take the caster 100 pts / (10 pts per day) = 10 days of action.
6th level caster example
A 6th level full caster would similarly generate 24 points per day. In 4–5 days of action they could generate enough affinity for an object that recharges a level one spell each day.
However, if the caster frequently casts 3rd level spells like protection from energy and maintains concentration for a full hour (12 affinity), they could generate much more affinity.
This generates great gameplay tension when a caster is spending their high level spell slots for their pet project and the team is like, "knock it off, you fool, and save us!"
Balance
In terms of game play balance, for both the 3rd level and 6th level wizard examples, 2-3 gaming sessions gets the character a magical device appropriate to their level–not too powerful, but good enough to be excited about.
2. Capacity
A caster has spell slots that represent how much magical energy they can hold. As they gain experience, they become a deeper well for arcane or divine power. Similarly, objects have a finite magical capacity that will set the maximum level of a spell they can hold, or equivalently the number of charges of a lower-level spell.
Capacity is determined primarily by an object’s value. This becomes one of the main motivators behind questing.
The rarer and more valued an item is, the higher its arcane capacity. It’s as if arcane power has its own sense of greed, or perhaps pride. Doubling value increases capacity by one spell level.
Spell capacity per level vs. value
| Value | 1st | 2nd | 3rd | 4th | 5th | 6th | 7th | 8th | 9th |
| 50 gp | 1 | -- | -- | -- | -- | -- | -- | -- | -- |
| 100 gp | 2 | 1 | -- | -- | -- | -- | -- | -- | -- |
| 200 gp | 3 | -- | 1 | -- | -- | -- | -- | -- | -- |
| 400 gp | 4 | 2 | -- | 1 | -- | -- | -- | -- | -- |
| 800 gp | 5 | -- | -- | -- | 1 | -- | -- | -- | -- |
| 1600 gp | 6 | 3 | 2 | -- | -- | 1 | -- | -- | -- |
| 3200 gp | 7 | -- | -- | -- | -- | -- | 1 | -- | -- |
| 6400 gp | 8 | 4 | -- | 2 | -- | -- | -- | 1 | -- |
| 12800 gp | 9 | -- | 3 | -- | -- | -- | -- | -- | 1 |
Loading and Overloading
A magic item can be repeatedly charged with spells up to its capacity. However, by spending additional spell slots, a spellcaster can overload an object with additional single uses charges equal to their spellcasting ability modifier, subject to the following conditions which prevent abuse:
- To overload, all extra spell slots must be loaded at once.
- Each overloaded charge adds a 10% chance of the object breaking and losing its value (capacity) after spending the last overloaded charge.
- Overloaded changes must be spent before an item can be overloaded again.
Overloading example
Consider a 200 gp item. It has capacity of 3 charges. A wizard with +2 intelligence modifier can cram in two additional charges, for a total of five charges. The object will have a 20% chance of breaking after spending the 2 overloaded charges. More possibilities are shown in the following table as an example.
| Loading | +1 | +2 | +3 | +4 |
|---|---|---|---|---|
| Breaks after spending last overloaded charge? |
10% | 20% | 30% | 40% |
| Charges | ||||
| 1st level | 3 | 4 | 5 | 6 |
| 2nd level | 1 | 2 | -- | 3 |
| 3rd level | 1 | -- | -- | 2 |
| 4th level | -- | 1 | -- | -- |
| 5th level | -- | -- | 1 | -- |
| 6th level | -- | -- | -- | 1 |
| 7th level | -- | -- | -- | -- |
Single use: origin of the 1/10th rule
For single use, a caster can pack a single spell into an object with 1/10th of the capacity required for a self-charging item. This is the limit for a single use item as it gives a 100% chance for the object to be rendered unusable after spending the charge.
If we can make a single-use magical object with 1/10th capacity, but provide enough affinity, it seems reasonable we can make a single use magical object with minimal affinity, but provide enough capacity. The two most common single-use magical items are, in fact, these two extremes.
Potions: High capacity (expensive) and low affinity item
A potion has capacity deriving from the value of the ingredients. The magic is intrinsic so a mage doesn’t have pack it in. Even a nonspellcaster can make a potion. So, a potion is an expensive way to store magic, but requires minimal affinity.
Spell scroll: Low capacity (cheap) item with affinity
The time the magician spends with the scroll grant it a level of affinity sufficient to hold the spell. However, a spell scroll has the low value of ingredients: parchment and ink, so it has very low capacity. So, scrolls are fundamentally “overloaded”. This is why scrolls can’t be recharged.
Between those two extremes there are host of options for overloaded items, items that hold multiple chages, self-charging devices and devices that self charge multiple charges per day. See the Affinity and Capacity Chart for a high level summary. Basicall, you add capacity (value) for more charges or higher level spells and you add affinity for more self-charging and stability.
Caster time value
It is useful to interpret the wizard’s work time as having value and that value "buying" capacity, or equivalently affinity.
For example, one can consider a spell scroll as being made more rare and valuable by the application of a wizard’s valued time and attention. If a 1st level wizard’s time is worth 10 gp per day and that goes up by 1.8x each spell casting level, then the time required to create a scroll is as shown in the table.
The 1.8x scaling makes it so low-level wizards “tap out” sooner, meaning (realistically) they can’t add value for as long.
Notably, the timelines to generate spell scrolls are short enough to be relevant to a campaign. It also seems reasonable that a great wizard should be able to crack out a fifth level spell scroll in a half a day of work to remove a curse and charge someone 1000 gp as a marked-up price.
Spell scroll creation time (work adds value interpretation)
| Scroll time |
Caster max spell level |
1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 |
|---|---|---|---|---|---|---|---|---|---|---|
| Spell level | Work rate | 10gp | 18gp | 32gp | 58gp | 105gp | 189gp | 340gp | 612g | 1102gp |
| 1st | 50 gp | 5 days | 2.8 days | 1.5 days | 4 hrs | <3 hrs | <1 hr | <1 hr | < 1hr | <1 hr |
| 2nd | 100 gp | 6 days | 4 days | 1.7 days | 1 day | 4 hrs | <3 hrs | <3 hrs | <1 hr | |
| 3rd | 200 gp | 7 days | 3.4 days | 1.9 days | 1.1 days | <5 hrs | <3hrs | <3hrs | ||
| 4th | 400gp | 6.8 days | 3.8 days | 2.1 days | 1.2 days | <6 hrs | <4 hrs | |||
| 5th | 800 gp | 7.6 days | 4.2 days | 2.4 days | 1.3 days | <6 hrs | ||||
| 6th | 1600 gp | 8.5 days | 4.7 days | 2.6 days | 1.5 days | |||||
| 7th | 3200 gp | 9.4 days | 5.2 days | 2.9 days | ||||||
| 8th | 6400 gp | 10.5 days | 5.8 days | |||||||
| 9th | 12800 gp | 11.6 days |
Affinity and Capacity Chart
| Capacity | Minimum affinity (1/10x): single use |
Sufficient affinity (1x): self-charging |
Extra Affinity (>=2x): self-charging multiple charges |
|---|---|---|---|
| Minimum cost (1/10x) | Mundane | Spell scroll (10x overloaded, single use) |
capacity too low to self-charge |
| Sufficient value (1x) | Potion | 1x charging (can be temporarily overloaded) |
2x charging: multiple charges or higher level spell (can be temporarily overloaded) |
| Extra value (>=2x) | Higher level spell effects or more uses |
Multiple charges (stable) Self-charge 1x per day up to multiple charge capacity |
Self-charge multiple charges per day up to multiple charge capacity |
Self-charging item
An item with sufficient capacity and affinity acquires a charge every day up to its capacity. If there is enough extra affinity, the object can acquire multiple spell charges per day. Items cannot overload themselves. They can only be overloaded from a source of higher affinity like a spell caster.
Consider a 3rd level glyph of warding spell. The spell requires 200 gp of diamond dust. This value buys just enough capacity to infuse a 3rd level spell effect like explosive runes. The object you put the glyph on nominally has no arcane affinity until you cast on it (minimal affinity), so this is an unstable spell, which is why the infused object can’t be moved.
Spell materials cost discounts for caster time and effort
According to our prior calculations for wizard work value, if a 5th level wizard does a day of work on a glyph, that work value of about 100 gp would make it so the spell only requires 100 gp of diamond dust.
Affinity and stabilty
If the item we put the glyph on has sufficient affinity, the spell would be stable and movable. For a single use item we only need 1/10th of the regular 3rd level affinity of 300 pts meaning we need 30 pts for a single use 3rd level magic item. 30 pts can of affinity can be accumulated in 1.5 days of casting for 5th level wizard. So, the wizard can spend a day and some change in their workshop can spend 100 gp of diamond dust to create a movable glyph of warding.
Alternatively, the wizard can campaign for a day or two, using a rod as a focus to collect 30 pts of affinity, then return to the tavern, slap some runes on there in an hour of work, sprinkle it with the full 200 gp of diamond dust, spend the spell slot and have themselves a movable glyph of warding.
Healing should be expensive
Since objects imbued with healing spells reduce interdependency on other players, the DM should impose a harsh 1.5-2x overloading limit on affinity for healing spells. Make an excuse like, “Healing magic has to be more stable.” Do likewise, as needed, for any potentially game-busting spell like fireball, animate objects, or hypnotic pattern.
Cantrip infusions
Since a cantrip is effectively a ½ level spell, it should be correspondingly easier to construct single-use cantrip devices. Continuously operable cantrip casting magic items take a little more figuring. In a typical day of action, a caster might use a useful cantrip five to ten times. On the generous side assume a ½ level spell times 5 times per day gives us an equivalent of 2.5 1st level charges (250 affinity points and capacity 2.5). So, a device that uses a cantrip at-will should have affinity and value-based capacity halfway between 2nd and 3rd level recharging spell item.
A 5th level cantrip is effectively a 1st level spell, and so on.
3. Permanence—how to create permanent spell effects
When you attempt to change reality with arcane power, it is like punching a pillow. When your fist pulls back, the pillow expands going back to the way it was. But if you squish a pillow enough, eventually it flattens permanently. The more frequently and regularly you affect a magical change, the more nature begins to take this as the true form. The magical change gains “permanence.” Another way to think of this is that a spell has a fading memory after it ends. If you recast the spell before the memory is completely gone, it doesn’t make the spell any easier, but it makes the spell last a little longer because the arcane magic doesn’t have to do as much work against reality.
Spell memory: the rule of ten
If a spell is recast before ten of its durations have expired, the spell effect retains a degree of permanence. If this is repeated ten times, the level of permanence increases. The following chart shows the effect of casting a spell like “alter self” successively where the exact same appearance is created each time the spell is cast. After 10 castings the spell effects stick around for 8 hours. After another 10 castings they stick around for an entire day. Reality is being stuffed into a new mold. Casting once a tenday for a year is enough to bump the spell up to a duration of the caster’s entire lifetime.
Example of spell permanence increasing by repeated casting
| # of castings | Spell Duration | Minimum frequency of casting | Example frequency of casting | Time to next level of permanence (total elapsed) |
|---|---|---|---|---|
| 1–9 | 1 hr | 2.4x/day (10 hrs) | 8hrs (3x/day) | 3.3 days |
| 10–19 | 8 hrs | 1/(3 days) | 1x/day | 1 tenday (13 days) |
| 20–29 | 1 day | 1x/tenday | every other day | 2 tendays (33 days or ~1 month) |
| 30–39 | 1 tenday | 1x/(3 months)) | 1x/tenday | 100 days (133 days or ~4 months) |
| 40–49 | 1 month | 1 month | 1x/(10 months) | 1x/tenday |
| 50–69 | 1 yr | 1x/10 yrs | 1x/tenday | 100 days (11.1 months) |
| 70–79 | 10 yrs | 1x/century | 1x/tenday | 100 days (14.4 months) |
| 80–89 | 100 yrs | 1x/millennium | 1x/tenday | 100 days (17.7 months) |
| 90–99 | 1000 yrs | 1x/10,000 yrs | 1x/ month | 10 months (27.7 months) |
Teleportation circle example
Consider a teleportation circle with 8 hr duration. Cast it once per day for a tenday, then every other day for 20 days, then once a tenday for a year or so and your portal will last lifetimes. So, clearly, if you cast it every day for a year, as specified in the spell description in the Player's Handbook, it will last indefinitely. But that is hopelessly tedious and makes for awful gameplay. No campaign lasts long enough to worry about whether a spell duration is longer than 10 years. And no campaign can function while a caster needs to keep hopping back to an area to use a high level spell to create a portal.
From a minimalist perspective, to create a permanent portal, cast it every day for a tenday, then every other day for few tendays, then once a tenday for three months and then once a month for the rest of the year and you have a portal you can maintain by casting the spell teleportation circle once a year.
Expiration and loss of permanence
With permanence of 1 year, you can skip 9 years, come back, recreate the portal and it will still last a year. If you wait longer than that period, the permanence drops back to zero. Nature has finished healing your deformation. Why? Imagine that over the course of ten years the duration drops to a month, 10 months later it drops to a tenday, 3 months later drops to a day, a tenday later it drops back to normal. So, if you miss that window, it’s basically gone completely. To keep it simple if you miss the 10x duration time window, you start over.
4. Complexity: imbuing intelligence
By empowering it with a spell, a magical object can be imbued with its own rudimentary intelligence or “matrix," just as is achieved in spells such as a tiny servant, simulacrum, or animate objects. When you cast a spell, an animated object draws its principles of action from a reflection of you, just as the echo of a soul does when the spell speak with dead is cast. Just as your reflection is limited by the quality of the mirror, so the intelligence of a magical object will depend on the number of "layers" in its magical matrix.
If a tiny servant is a like a black and white image, a simulacrum is like full color. The higher-level spell gives a simulacrum more layers of realistic depth which captures more powers of cognition.
Spell level vs. construct intelligence
- 1st–3rd level = Programmed/instinctual (Int 0—4)
- 4th–6th level = Intuitive/intepretive (Int 5—7)
- 6th–9th level = Innovative/enterprising (Int 8—12)
Spell stacking
To imbue an object with more magical intelligence, we can either cast a higher-level spell, or stack different lower-level spells. However, two different 1st level spells reflect some of the same “color” layer and so they don’t add as much depth to a magical creation as a single 2nd spell. The penalty for stacking lower-level spells is an extra spell, or three for the price one. So three 1st level spells equals the complexity achieved by a 2nd level spell. Three 3rd level spells gets you 4th level spell complexity.
Spell stacking limit: 6 spells
The practical limit for spell stacking is 6 spells, which increments two spell levels of complexity. For example imbuing six 2nd level spells bumps the complexity of a construct up to 4th level.
The reason for this is clear. No amount of low level healing spells could bring someone back from dead. To access greater power over the mind, fate, life and reality, higher-level spells are needed. From this perspective, it is easy to see why simulacrum is a 7th level spell and you can’t create one by combining the spells tiny servant and enlarge. There are layers of definition of existence: identity, purpose, understanding, and capability the lower-level spells can’t pick up and reproduce.
Magical item examples
As an example, consider the Artillerist Artifcer's magical canon. What would it take to create this as a magical item?
Making the Artillerist's Cannon
Cannon features
- Physicality: movement, high AC, 5th level HP, 1 hour duration, and obedience
- Spell effects: flamethrower, ballista, and protector mode
As a bare-bones example, we'll consider an item we can use once per day. And we'll choose one mode of operation.
The behavior, AC, HP and duration are similar to summon beast, a 2nd level spell. So we'll need sufficient affinity and capacity for self-charging and storing a 2nd level spell per day.
The flamethrower and ballista actions act like cantrips being cast at 5th level or roughly a 1st level spell. Using our previous assumption of a cantrip being used about five times per day, we'll need enough capacity and affinity to charge five 1st level spell slots.
Flamethrower/force ballista construct
| Spell | level | slots | affinity | capacity (value) |
|---|---|---|---|---|
| summon beast | 2nd | 1 | 200 | 2 (100 gp) |
| burning hands/ catapult |
1st | 5 | 500 | 5 (800 gp) |
| Total | 700 | (1000 gp) |
Notice that we didn't just add 5x 50 gp = 250 gp for the cost of the burning hands/catapult spell capacity. We established earlier that capacity for a 5th level spell is equivalent to capacity for five first level spells. So add up the capacity, convert it to a spell level and use that value (800 gp).
When we have different spells, it is equivalent to creating two different items and stapling them together, so the values don't stack.
Note, it is much cheaper to make several one-use items than it is to make one multi-charge item. This is why many magical items are single use. If you have something super valuable, why not use it for a single high level spell?
Affinity of 700 could be accumulated by a 6th level wizard generating 24 affinity points per day in about 30 days, 10-12 sessions, or 3-5 levels of advancement.
That sounds about right for a self-driving, kick-butt cannon you can use as a bonus action (~feat). DMs, note that if this is taking too long, let the caster find an object with high affinity, for instance the spellcasting focus of a powerful caster they defeated. Then the task becomes much easier. They only need craft the focus into a construct with enough value (capacity) to hold the spells.
As another example, a druid or could have a staff that conjures a beast that hurls stones with tremendous force. It doesn't need to be a steampunk gadget like what the artificer uses.
Making a life-saving amulet
There are two ways to do this. We could make an item that self-charges a single use of the cantrip spare the dying. You would use a command word and touch it to a dying creature.
Lame. Might as well do a medicine check.
A better device would be an amulet that recognizes when the user is dying and casts the cantrip automatically. That lets your team keep fighting rather than attending to you. But, it's a step up in intelligence, so we'll need to find a spell that can sense whether something is alive.
This feels like divination magic and detect poison and disease sounds like a good candidate. It's a 1st level spell and it has a duration of 10 minutes. However the range is 30 ft. If it is on the user's chest, we only need 1 ft. of range to detect a heart stopping. That means we can divide the range by 30x and increase the duration by 30x up to 5 hours. You can bargain some extra duration here, because the spell only needs to detect one kind of disease: heart failure. So that nets us another factor of five (this is where you argue with your DM), for about a day's worth of duration. Argue it this way: we reduce the range for an increase in duration to 8 hrs and reduce the spell functionality for an increase in duration to 24 hrs.
Amulet of Life Sparing
| Spell | level | slots | affinity | capacity (value) |
|---|---|---|---|---|
| spare the dying |
cantrip (1/2) |
1 | 50 | 25 gp) |
| detect poison/ and disease |
1st | 1 | 100 | 1 (100 gp) |
| Total | 150 | 125 gp |
This amulet will require a gem of 100 gp plus a 25gp setting of silver into which you can scribe glyphs of spare the dying and detect poison and disease, such that when heart failure is detected, the glyph triggers spare the dying. It should require some research/stealing books to figure out how to modify the detect poison and disease spell, or do some dirty work for a powerful wizard in exchange for tutoring. This is all good role playing and will get you into lots of fun trouble.
As a 3rd level wizard accumulating about 10 pts of affinity per day, you could create an arcane focus powerful enough to self-charge in about 15 days of action–faster if you level up during that time.
If you just wanted a single use trinket for an upcoming confrontation, you would need 1/10th of the affinity–a day and half of casting to get that.
Making a +1 weapon
There is a spell that does exactly this: magic weapon. (If there wasn't a spell for this you might be able to cobble together a combination of lower-level spells that increase damage like hunter's mark or divine favor with something that makes you more likely to hit like true strike or bless. You would trade range and bonuses and/or number of targets to increase the duration.)
Making it
First, we'll need an item with 200 affinity to recharge one 2nd level spell each day. Then we need to get the duration of the spell up from one hour to 24 hours.
Let's get an artificer to glyph the spell magic weapon onto a sword or mace or whatever.
Now if we cast 10 scrolls or scribe 10 glyphs of magic weapon the course of a day, the permanence of the spell increases to 8 hrs. So, now the sword can be triggered for 8 hours per day. Another 10 castings once every day for 10 days boosts the permanence to 24 hrs, and it becomes self-charging.
Casting and concentrating on magic weapon for one hour generates 4 x 2 = 8 affinity per casting. 20 casting generates 160 affinity. Throw in an arcane focus or weapon on which a paladin has cast a few spells and you'll soon have 200 affinity.
For the spell scroll/glyph cost, we'll use the 2nd level spell capacity value of 100 gp doubled to 200 gp (for a profit for whichever artificer we buy them from.)
+1 Weapon
| Spell | affinity added | capacity (value) |
|---|---|---|
| 20 scrolls/glyphs of arcane weapon | +160 | 20 x 200 = 4000 gp |
| Weapon | 50 gp | |
| Arcane focus | +40 | 50 gp |
| Total | 200 | 4100 gp |
40 affinity points costs a 6th level caster generating 24 affinity points per day, about 2 days of action or about 1 campaign session.
+2 weapon, etc.
It is pretty straightforward to scale up to a +2 or higher weapon. The spells just need to be up-cast. Double each spell affinity and capacity value and spell scroll cost you have have a +2 weapon.
Change Log
| Date | Change |
|---|---|
| 2023.03.28 | Added note on higher level cantrips |
| 2022.02.10 | Initial release on gmbinderc.com at https://www.gmbinder.com/share/-MvX7gFUJzueb4WVWhpJ |
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