Oath of Perdition

Paladins of the Oath of Perdition take on an Oath to cleanse all the worlds and planes from the pestilence that is fiends and do not shy away from using any measures and powers to achieve that goal. As such, when they take on this Oath they let an immaculate amount of infernal energy into their bodies, changing them beyond return and allowing them to temporarily transform into the Demonic and Devilish forms to even the odds against those they swore to exterminate.

Oath Tenets:
- The greater good above all else. No personal sacrifice that you or others can make is too great.
- Power is a necessity if evil is to be cleansed.
- I will not be fully corrupted by the dark powers I call upon. No matter what I must do to ensure it.

Oath Spells and Casting

Oath of Perdition Paladins use their inner connection to the nine hells and the abyss to manifest fiendish magic around them, using power of the lower planes to achieve results many spell casters use years of study to copy. Doing so, however, does not come for free, as with each spell cast a small bit of their humanity slips away and paladins that devote themselves to the fiend hunt too much may not realise they have become the very thing they swore to destroy.

Your connection to the fiends makes it so you always have certain spells ready; when you reach a Paladin level specified in the Oath of Castigation Spells table, you thereafter always have the listed spells prepared and they do not count towards the maximum amount of spells you can prepare

Paladin Level	Spells
3	Hellish Rebuke, Devil's Due
5	Veil of the Reaper, Recall
9	Zippit!, Haste
13	Arcana's Hotfix, Consuming Pyre
17	Mirrored Agony, Steel Wind Strike

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Fiendish Transformation

When you reach level 3 and choose this Oath, it compels you to fight the fiends with the use of their own powers. When you deal fire, radiant, necrotic or psychic damage to a hostile creature roll a d20 after each instance of damage: On a roll of 1, you undergo a transformation into an Abyssal Demon, on a roll of 20 you undergo a transformation into a Hellish Devil.

While in your Demonic form you gain resistance to all types of damage, other than bludgeoning, piercing and slashing, you grow one size larger than your normal form (large, if you were medium) and you gain a bonus to your Armor Class equal to your Charisma modifier, as massive spikes and protective carapace manifests around you..

While in your Devilish form your base walking speed is doubled and you gain flight speed equal to your walking speed, as two leathery bat like wings sprout from your back. Additionally while in your Devilish form, your movement does not trigger attacks of opportunity and whenever you take an attack action you may make another attack as part of the same action.

Regardless of the form you transform into, while under the effects of the Fiendish transformation your creature type is Fiend. If the Fiendish Transformation was triggered during your turn, you gain the effects of the Fiendish Transformation until the start of your next turn. If the Fiendish Transformation was triggered on another creature's turn, the effects remain until the end of your next turn. While under the effects of Fiendish Transformation you cannot roll a d20 to check whether you undergo another Fiendish transformation.

Finally, as a bonus action you may expend a use of your channel divinity to strengthen your connection to your inner fiend. For the next minute or until you trigger your Fiendish Transformation, after you roll a d20 to check wether you undergo a Fiendish Transformation, you may choose to add or subtract a 1d4 to the result of the roll. If the total result is 1 or lower you may treat it as a natural one, if the total result is a 20 or higher, you may treat it as a natural 20 for the purposes of your Fiendish Transformation

Aura of Perdition

At 7th level, you are able to channel your immaculate hatred for Fiends to grant powers of your oath onto your allies. As such, all creatures of your choosing inside of your Aura of Protection gain access to the Divine Smite and Ballistic Smite spells, and are able to cast one of them once per round of combat without requiring a spell slot to do so. If you are in your Fiendish Transformation, the level at which the Divine Smite or Ballistic Smite is cast when it is cast this way equals your Proficiency Bonus.

Power of the Lower Planes

At 15th level, your connection to the Nine Hells and the Abyss grows, you able to use more of their powers and morph into your fiendish form more consistently. Your Fiendish Transformation feature now also triggers on rolls of 2 (for Demonic form) and 19 (for Devilish form) when making a d20 test.

Additionally, while you are in your Demonic form you are considered as being under the effects of Spiny Shield spell, upcast at a level equal to your Proficiency Bonus, as massive spikes grow from your entire body. While you are in your Devilish form, you may replace one of your attacks each turn with a casting of Scorching Ray as beams shoot from your eyes, without using a spell slot, upcast at a level equal to your proficiency bonus. If you have any magical effects that affect damage of your attacks, they also apply to the damage of these spells.

Blade of the Infernos

At level 20 you have reached the pinnacle of your Oath, and as such, you are able to become the very thing the Fiends fear more than death by utilising their own power: The Blade of the Infernos. At the beginning of your turn (no action required) you can empower your connection to the Abyss and Nine Hells and gain the following benefits for the next minute or until you fall unconscious or die:

You gain blind sense out to a range of 30 ft and are able to see into the ethereal plane for this distance

You can still roll a d20 under the rules of Fiendish Transformation when under the effects of your Fiendish Transformation. You can only be under effects of one Fiendish Transformation at a time, and, as such, if you roll a Demonic Transformation while in your Devilish form or vice versa all abilities and effects granted to you by your previous form end, unless you expend a use of your Channel Divinity to maintain your current form.

After you use this feature you cannot use it again until you finish a long rest.