You bear the mark of a Pit Lord, granting you several of the powers normally enjoyed by warlocks. That's where your connection to the Nine Hells ends, though. The Pit Lord doesn't watch over you, protect you, or probably even know you exist. Do what you will with your ill-gotten power, but be aware that, should you ever cross paths with your absentee patron, how it reacts depends on what you've done up until that point.
Spellcasting
When you reach 3rd level, you augment your martial prowess with the ability to cast spells. See chapter 10 for the general rules of spellcasting and chapter 11 for the warlock spell list.
Cantrips. You learn two cantrips of your choice from the warlock spell list. You learn an additional warlock cantrip of your choice at 10th level.
Spell Slots. The Pact Knight Spellcasting table shows how many spell slots you have to cast your warlock spells of 1st through 4th level. The table also shows what the level of those slots is; all of your spell slots are the same level. To cast one of your warlock spells of 1st level or higher, you must expend a spell slot. You regain all expended spell slots when you finish a short or long rest.
For example, when you are 7th level, you have two 2nd-level spell slots. To cast the 1st-level spell witch bolt, you must spend one of those slots, and you cast it as a 2nd-level spell.
Spells Known of 1st-Level and Higher. You know two 1st-level warlock spells of your choice.
The Spells Known column of the Pact Knight Spellcasting table shows when you learn more warlock spells of 1st level or higher. A spell you choose must be of a level no higher than what's shown in the table's Slot Level column for your level. When you reach 13th level, for example, you learn a new warlock spell, which can be 1st, 2nd, or 3rd level.
Additionally, when you gain a level in this class, you can choose one of the warlock spells you know and replace it with another spell from the warlock spell list, which also must be of a level for which you have spell slots.
Spellcasting Ability. Charisma is your spellcasting ability for your warlock spells, so you use your Charisma whenever a spell refers to your spellcasting ability. In addition, you use your Charisma modifier when setting the saving throw DC for a warlock spell you cast and when making an attack roll with one.
Spell Save DC = 8 + your proficiency bonus +
Spell attack modifier = your proficiency bonus +
Pact Knight Spellcasting
| Level | Spells Known | Spell Slots | Slot Level |
|---|---|---|---|
| 3rd | 2 | 1 | 1st |
| 4th-6th | 3 | 2 | 1st |
| 7th-9th | 4 | 2 | 2nd |
| 10th-12th | 5 | 2 | 2nd |
| 13th-15th | 6 | 2 | 3rd |
| 16th-18th | 7 | 2 | 3rd |
| 19th-20th | 8 | 2 | 4th |
Pact Weapon
As a free action, you can create a pact weapon in your empty hand. You can choose the form that this melee weapon takes each time you create it (see chapter 5 for weapon options). This weapon counts as magical for the purpose of overcoming resistance and immunity to nonmagical attacks and damage.
Your pact weapon disappears if it is more than 5 feet away from you for 1 minute or more. It also disappears if you use this feature again, if you dismiss the weapon (no action required), or if you die.
You can transform one magic weapon into your pact weapon by performing a special ritual while you hold the weapon. You perform the ritual over the course of 1 hour, which can be done during a short rest. You can then dismiss the weapon, shunting it into an extradimensional space, and you can choose for it to appear whenever you create your pact weapon thereafter. You can't affect an artifact or a sentient weapon in this way. The weapon ceases being your pact weapon if you die, if you perform the 1-hour ritual on a different weapon, or if you use a 1-hour ritual to break your bond to it. The weapon appears at your feet if it is in the extradimensional space when the bond breaks.
At 7th level, when you gain the Improved Pact Weapon invocation (see below), you gain an additional benefit: you can create any ranged weapon you are proficient with, and when you do you also create ammunition to use with them. You can also choose to create two one-handed melee weapons, one in each hand.
Eldritch Invocations
In your study of occult lore, you have unearthed eldritch invocations, fragments of forbidden knowledge that imbue you with an abiding magical ability.
At 7th level, you gain one eldritch invocation of your choice. A list of the available options can be found on the Optional Features page. You also gain the Improved Pact Weapon invocation at this level. You gain additional invocations at 13th and 19th level.
Additionally, when you gain a level in this class, you can choose one of the invocations you know and replace it with another invocation that you could learn at that level.
If an eldritch invocation has prerequisites, you must meet them to learn it. You can learn the invocation at the same time that you meet its prerequisites. A level prerequisite refers to your level in this class. You are considered to have the Pact of the Blade for meeting prerequisites.
Eldritch Strike
At 10th level, you learn how to make your weapon strikes undercut a creature's resistance to your spells. When you hit a creature with a weapon attack, that creature has disadvantage on the next saving throw it makes against a spell you cast before the end of your next turn.
Arcane Charge
At 15th level, you gain the ability to teleport up to 30 feet to an unoccupied space you can see when you use your Action Surge. You can teleport before or after the additional action.
War Magic
Starting at 18th level, when you use your action to cast a spell, you can make one weapon attack as a bonus action.
Notes on This Subclass
To highlight the martial emphasis on this class, the Pact Knight has more flexibility with their Pact Weapon feature.
For starters, they can bind an existing weapon but still create new ones out of thin air. This allows them to have a favorite weapon, but not be limited to using only that one weapon.
Second, unlike a warlock, a pact knight can conjure a weapon as a free action. This lets them draw and attack quickly, allowing them to react faster to unexpected battle. It also means they can switch weapons between attacks — useful if an enemy proves resistant to a particular damage type, or if they want to quickly switch from a ranged weapon to melee.
Pact knights automatically get the Improved Pact Weapon invocation at 7th level, giving themselves an additional bonus to attacks and also letting them conjure ranged weapons.
Note that pact knights do not get the Hex Warrior feature of hexblades; it is assumed that a pact knight is going to emphasize Strength or Dexterity over Charisma, given that they had to go two levels using mundane weaponry.
Thanks to Nathan Knaack for the idea on the inattentive demonic patron.