Oath of the Forbidden

In the hidden depths of chaos, beyond the confines of Twilight, exist many chaotic gods, eldritch entities, and abominations that transcend the comprehension of mortalkind. They seek to reach into the Twilight, making a place for themself, but they are just too dangerous. Hence, these otherworldly entities must never be let inside the realms, and many traces of their history were destroyed. You, on the other hand, had defied this understanding and approached this Lovecraftian tradition, communicating their ancient secrets. The whispers of the forbidden echo within your heart, as you slowly lose more and more of the normalcy that keeps you sane.

The Oath of the Forbidden had forsaken any belief in the righteousness of the gods' words and promises, as they defected to the forces that do not exist in the world, potentially causing apocalypse and destruction if this otherworldly power manages to slip into any realms. Because of this, these paladins could easily be marked as a heretic, a taboo criminal, and an abomination of the gods themselves by those who worship a deity.

Level 3: Eldritch Magic

The Eldritch Blast is always prepared for you. Your Divine Smite is replaced with a unique spell called Otherworldly Smite

Otherworldly Smite

Casting Time: Bonus action, which you take immediately after hitting a target with a Melee weapon or an Unarmed Strike
Range: Self
Components: V
Duration: Instantaneous

The target takes an extra 1d8 Necrotic and 1d8 Psychic damage from the attack. The target is grappled if they are concentrating on a spell.

Using a Higher-Level Spell Slot. The damage increases by 1d8 for each spell slot level above 1. You can decide if this damage increase be Necrotic or Psychic damage.

 

Level 3: Forbidden Constitution

Your body is altered by powers beyond all worlds. All of your Saving throws you are not proficient with have their bonus reduced by your Proficiency bonus (except death save).  For each two bonuses affected this way, you gain the ability to succeed a failed Saving throw, refreshed after finishing a Long Rest.

At 15th level, when you choose to succeed on a Saving throw using this ability, you may also cast a smite spell and make a melee attack against the triggering creature. You do not make an additional attack with this feature through the Elite Paladin boon.

Level 3: Oath of the Forbidden's Spells

The cursed magic of the otherworld will always seek to be used and cast by you; when you reach a Paladin level specified in the Oath of the Forbidden's Spells table, you thereafter always have the listed spells prepared.

Oath of the Forbidden's Spells

Level 7: Aura of Mindbreaking

Your Aura of Protection becomes infested with eldritch horrors, granting you additional properties while you are not unconscious. When an enemy creature makes a Saving throw within your Aura's range, its bonus is reduced by 1d4. At 15th Paladin level, this becomes a d6, and at 20th, it becomes a d8. This reduction does not work against Gargantuan or Aberration-type creatures.

When a creature makes an Intelligence saving throw within your Aura, you can use your reaction to infest the creature's mind with incomprehensible concepts. The target creature takes psychic damage equal to their Saving throw roll, and if they used a legendary resistance, this damage is doubled.

Level 15: Corrupting Resilience

Once per turn, when you are hit with an attack, you can expend any amount of your hit dice and increase your AC for that specific attack instance by the rolled amount. When you roll a hit die this way, you reduce your maximum hit points by the rolled amount until you finish a Long Rest, and this reduction cannot be ignored.

Level 20: Chthonic Descent

As a Bonus Action, you open your body to the otherworldly entities to possess, granting you immense power at a great cost for 10 minutes. Once you use this feature, you can't use it again until you finish a Long Rest. You can also restore it by expending a level 5 spell slot (no action required).

• Otherworldly Desires. At the start of your turn, any unconscious creature within your Aura must succeed on a DC 20 Charisma saving throw or be possessed by eldritch entities, regaining 1 hit point. These possessed creatures will be under your control unless the DM wants to control them. This effect cannot affect Aberrations or CR 21+ creatures, or creatures immune to possession.
• Mental Vulnerability. Any time a creature within 30 feet of you takes psychic damage, you can choose to pierce through their mental resistance. The target must succeed on an Intelligence saving throw or be vulnerable to psychic damage for that specific damage instance.,
• Eldritch Tentacles. Once per turn, you can replace your weapon attack's damage with psychic damage. You can choose to grapple creatures from 60 feet away. Creatures grappled this way are considered to be within your melee reach for attacks and your touch range for spells.