Esoteric Monsters
This is a system of templates to makes monsters more dangerous, unique and memorable. In essence, it makes them exceedingly hard to damage outside of a specific esoteric weakness. Battles with this monsters often play out as one part fight and one part puzzle - tackling these monsters without research and preparation is often all but impossible and they should not be carelessly unleashed on an unprepared party.
Remember, it is up to the DM to make the encounter possible ny providing the tools and clues to win.
Immunity Grade
The first element of an Esoteric Monster is to make it far harder to kill with traditional means. This is a template placed on top of the monster's other stats, and comes in the levels found below. In the following table "DR" stands for "Damage Reduction"; damage reduction is a rarely used mechanic in 5e (for good reason) but is appropriate for what we are trying to do here, and is subtracted from any damage done to a creature before any other effect takes place.
| Immunity Grade | Effect |
|---|---|
| Low | The creature has a DR of 10. |
| Moderate | The creature has immunity to bludgeoning, piercing and slashing damage, a DR of 15, immunity to spells 5th level or below, and Legendary Resistance equal to its proficiency bonus. |
| Absolute | The creature has immunity to all damage types, is immune to all magic effects, and has unlimited use of Legendary Resistance. |
Magic Resistance grants advantage on saving throws against magical effects. The purposes of Immunity Grade, magical effects include effects from Magic, Spells, Psionics, Ki, and other supernatural sources.
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Esoteric Weakness
At the heart of this concept and style of design is that these creatures possess a fatal flaw that renders them vulnerable. An esoteric weakness can range from a convenient way to bring down the monster to the only real way to harm the creature.
You can roll from the table below, or select one that is appropriate to the creature (or even make your own that fits the creature and narrative!)
| d20 | Esoteric Weakness |
|---|---|
| 1 | Standing in moonlight. |
| 2 | Weapons forged more than 100 years ago. |
| 3 | Called shots targeting their ankle. |
| 4 | Poison from Foxglove flowers. |
| 5 | Divination magic. |
| 6 | Mithral weapons |
| 7 | Acid damage |
| 8 | Silvered weapons. |
| 9 | Environmental damage. |
| 10 | Piercing damage from a good aligned creature. |
| 11 | A weapon of significance to the creature |
| 12 | Thunder damage. |
| 13 | A damage type the creature has never taken. |
| 14 | Damage dealt during the creature's turn. |
| 15 | Weapons covered in blood. |
| 16 | Extra planar creatures. |
| 17 | Damage dealt by creatures that cannot see it. |
| 18 | A specific spell created to defeat it. |
| 19 | Any damage for a round after speaking its true name |
| 20 | A specific artifact. |
Damage dealt in the condition that matches a creature's weakness bypasses it's immunity grade effects. For example, if a creature's esoteric weakness is moonlight, if it takes damage while in direct moonlight, it would be vulnerable to that damage and that damage would bypass it's immunity grade.
A creature's vulnerability to its weakness is inversely proportional to it's immunity grade; a creature always has vulnerability to damage dealt in a way that matches its weakness, but a creature with a moderate or absolute immunity grade additionally treats any damage dealt by it as an automatic critical hit.
Source of Power
One consideration that should always come up in this sort of encounter is the source of the monster's immunity grade, esoteric powers, and esoteric weakness.
For a low immunity grade, perhaps it is a goblin that blessed (or cursed) by a powerful fey or spirit. This sort of fight can be overcome without learning its weakness (as long as the immunity grade is low). An absolute immunity grade is usually the boon of a god and is often given to a suitably epic recipient, though not always. An encounter against a goblin Achilles with an Absolute immunity grade would be memorable!
Other frequent sources include beings from the far realm to which normal logic does not apply, fey creatures that follow their own rules, or "a wizard did it".
Clues
A critical part of running an esoteric monster is cluing the party into the fact that you are running an esoteric monster. The first time a monster like this is used, it's not a bad idea to simply tell the players (particularly ones familiar with 5e combat) that they will encounter a monster that follows unique rules and warn them they will need additional information to fight the monster.
You can (and should) offer less fourth wall breaking clues. Terrified tales of a creature that cannot be injured. Reports of arrows bouncing off it harmlessly, it leaping through walls of fire unscathed, etc.
A popular technic is to let the party fight it briefly, but have it disengage, running away - it is not interested in the party. They may choose to hunt it, but if they wish to, they'll have to figure out why their attacks seemed to do nothing to it.
Challenge Rating
The challenge rating system provides no real tools for engaging a monster like this, as it's challenge rating is intentionally excessive when its weakness is unknown, and often weaker than its more mundane counterparts should the players be prepared for it. This template has no standardized impact on the creature's CR.
That said, a DM should consider that these fights have an extra element of challenge to them that is not reflected in the CR system and take that into consideration when deploying monsters of this type.
Special Powers
The following are not necessarily to build an esoteric monster, but can add to the challenge and serve as the basis for making the monster a larger threat, or more difficult to deal with. Some groups may have little trouble dealing with a monster that is simply hard to kill, so adding a few of these can ensure that an esoteric monster remains an appropriate challenge. You can either roll on the table, or select powers that may vex your player's favorite tactics:
| d8 | Special Powers |
|---|---|
| 1 | At the start of each of its turns, the creature teleports 5 feet in a direction of its choosing. |
| 2 | As a reaction to taking damage that doesn't trigger its esoteric weakness, the monster enters the ethereal plane until the start of its next turn. |
| 3 | The creature can add double its proficiency bonus to athletics checks, and can contest a grapple check at the start of its turns without expending an action. |
| 4 | The creature is exudes a supernaturally terrifying presence. Any creature that starts its turn within 30 feet of the esoteric creature while being able to see it must make a Wisdom saving throw (DC 8 + [2 x the creature's proficiency bonus]) or become frightened until the start of their next turn. |
| 5 | The creature gains the ability to cast any spell cast within 60 feet of it, gaining one use of that spell it can cast without expending a spell slot, mimicing the casters spell casting modifiers. |
| 6 | After a creature takes damage of a damage type not of its esoteric weakness, it absorbs further instances of that damage type until the start of its next turn (regaining hit points equal to the damage taken from it). |
| 7 | The creature is always invisible. |
| 8 | The creature gains a number of Legendary Actions equal to half its proficiency bonus (rounded up) that it can use to make a single attack available to it or move up to its movement speed (this should not be applied to monsters that already have Legendary Actions). |
Art Credits
- Licensed Stock Art (Shutterstock)
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