Oath of the Illrigger

Sacred Oath
Comments from the Knuckle: There were two motivations behind the creation of this subclass: 1) Balder’s Gate: Descent Into Avernus just came out, and I think it would be so much fun to play an infernal paladin in that campaign. Maybe you didn’t start out with ties to hell, maybe in another life your character would have been Oath of Devotion. But when confronted with the powers of an archduke, you swear fealty as a way of surviving the adventure. 2) I’ve been watching a lot of The Chain of Acheron, and wanted to write a blogpost as tribute to it, and as an excuse to tell people to go watch it. The Chain is a great stream, I 110% recommend you go watch it; Matt Colville’s a phenomenal Dungeon Master. On The Chain, one of the characters is a tiefling illrigger named Judge, and Matt built out a full 1-20 class that’s currently in its alpha testing on the stream. The Invoke Authority Channel Divinity option and Infernal Seal feature provided here are inspired by/based on features that Colville’s Illrigger gets. Sooooo…yeah, have fun playing Descent, and go watch The Chain.

Oath of the Illrigger

Illriggers are an ancient order of paladins that swear their allegiance to one of the Lords of the Nine, the archdukes of hell. In supplication to their infernal masters, they carry their lords’ command and lead their armies into battle to beat back the demonic horde. Such paladins hold their oaths with a fierce conviction, for they believe that, without people like them, demons would overwhelm the forces of hell and spill out into the other planes of existence, decimating every world like a plague.
     Oftentimes, an archduke will recruit soldiers and mercenaries from the Material Plane to join the ranks of the Illriggers, targeting individuals who have strong bonds with their brothers-in-arms. This way, should the archduke ever need supplemental forces for the armies of hell, they can call upon their loyal Illrigger, who in turn recruits their ardent allies to fight alongside them through hell and back.

Tenets of the Illrigger
The tenets of the Illriggers are kept secret, and used as a kind of passphrase between Illriggers so that they know they can speak freely, one infernal paladin to another.
     Hold the Line. Wherever demons are met, they must be eradicated. Their chaos must not be allowed to infect the Multiverse and tip the scales of the Blood War in their favor.
     Consolidate Power. Mortals on the Material Plane squabble for power, blind to the true threats of the multiverse. You’ve seen beyond the mortal veil, and choose to seek out and amass power in tribute to your archduke. Such conquest is among the most important tasks you have on the Material Plane.
     Judge, Jury, and Executioner. You swear to be the embodiment of your archduke’s will wherever you are. You are beholden to no law or master before them. If you see a course of action that would further your archduke’s goals, you will take it, consequences be damned.
     Unwavering Loyalty. Never forget who you swore fealty to. Be vigilant and maintain constant adherence to their will, for their vengeance shall be swift at even the mere thought of disobedience or treachery.

Bonus Language
Starting at 3rd level after you swear this Oath, you can speak, read, and write Infernal.

Oath Spells
You gain oath spells at the paladin levels listed in the Oath of the Illrigger Spells table. See the Sacred Oath class feature for how oath spells work.

Oath of the Illrigger Spells

Channel Divinity
When you take this oath at 3rd level, you gain the following two Channel Divinity options. See the Sacred Oath class feature for how Channel Divinity works.
     Infernal Implement. You can use your Channel Divinity to call to your hand a weapon from the arsenal of the archduke you swore your oath to. As a bonus action, you present your holy symbol and invoke their terrible name. In a flash of fire and brimstone, the weapon appears in your hand. This magic weapon can be any simple or martial weapon, and you gain a bonus equal to half your proficiency bonus (rounded down), to attack and damage rolls you make with this magic weapon. When you hit a hostile creature with this weapon, your weapon places a minor curse upon the creature. Until the beginning of your next turn, the creature subtracts 1d4 from attack rolls which target creatures other than you. Additionally, when you use your Divine Smite or Improved Divine Smite feature while wielding this weapon, you can cause those features to deal fire or necrotic damage instead of radiant. Your Infernal Implement persists until you take a short or long rest, at which point it melts into smoke and dissipates.
     Invoke Authority. As an action using your Channel Divinity, you can present your holy symbol and speak the terrible name of your archduke, forcing a devil that you can see within 30 feet of you to make a Wisdom saving throw. A devil with a challenge rating greater than half your paladin level (rounded down) automatically succeeds on this saving throw. On a failed save, the devil is bound to your will, as if a dominate monster spell had been cast upon them. This effect lasts for 1 minute, as long as you are on the same plane of existence as the devil. It ends early if the devil drops to 0 hit points.

Devilish Aura
Starting at 7th level, you emanate an aura of infernal might. The aura extends 10 feet from you in every direction, but not through total cover. Creatures within the aura feel its effects, but you yourself do not gain its benefits:

• Demons within your aura are placed under the effects of the bane spell.
• Friendly creatures deal an additional 1d6 fire damage when they hit with a weapon attack. Good-aligned creatures gain no benefit from this aura.

     At 18th level, the range of this aura increases to 30 feet.

Infernal Seal
Starting at 15th level, when you hit a creature with an attack, you can place an infernal seal on them as a bonus action. On any subsequent turn you can consume the seal as an action. Until the seal is consumed, the creature takes an additional 1d6 fire damage when you hit them with a weapon attack. When you use your action to consume the seal, the target must make a Constitution saving throw against your  paladin spell save DC or take 6d8 fire damage, taking half as much damage on a success. A creature who is slain while under the effects of your infernal seal has their soul condemned to the hells. Their soul is no longer free to return should a creature try to resurrect them by any means short of a wish spell.
     You can use this feature a number of times equal to your Charisma modifier. You regain all expended uses when you complete a long rest.

Legionnaire from Hell
At 20th level, you become completely consumed by the infernal powers of your Oath, which grants you the following benefits:

• You are immune to fire damage, and your native plane becomes the layer of hell that your archduke rules over.
• As a bonus action on your turn, you can cause hostile creatures within 30 feet of you to take 1d10 force damage.
• When you reduce a creature to 0 hit points with your Infernal Implement, you regain 2d10 + 10 hit points.