You've made a pact with a being of great filth and decay. You become their master of pestilence and decay, becoming a virulent destroyer of life. Their magics permeate through even the most holy, and nobody is safe.

The Blighted One

Your patron has infested you with disease. You are resistant to poison damage and have advantage on saving throws against the poisoned condition and are immune to further disease.

Additionally, you learn the cantrip Acid Splash, which counts as a warlock cantrip for you.

Vile Taint

Your plague spreads virulently. A creature can no longer be immune to your poison damage - they are now resistant instead. Likewise, a creature that is resistant to poison damage takes poison damage from you as normal.

If a spell or ability you use causes a creature to become poisoned, any creature within 5 feet must also make the saving throw or be poisoned.

Whenever you fall unconscious, a plume of vile disease exhumes from your body. Each creature within 5 feet must make a Constitution saving throw against your Spell DC or be poisoned.

Absolute Corruption

Starting at 10th level, your curses and banes cause terrible dread. If a creature is:

• under the poisoned condition by an effect or spell you created or
• affected by a spell requiring concentration from you

then creature is afflicted. An afflicted creature is incredibly weakened and reaching death at a rapid pace.

• Choose a damage type. The afflicted creature is now vulnerable to that damage type. If they were immune to that type, they are no longer immune and are instead resistant. If they are resistant, they are no longer resistant and take damage as normal.
• If the creature is bloodied, it must make a Constitution saving throw at the start of each of its turn against your spell DC. On a fail, it falls unconscious until the start of its next turn. Upon returning to consciousness, it does not have to make the save again until the following turn. (That is, it does not wake back up and immediately save again.)

Death's Embrace

You have become a being of pure decay and damnation. You can choose a creature within range to immediately become afflicted. You can only afflict a creature this way once per long rest.

Any afflicted creature that is unconscious and has less than 100 hit points must make a (constitution) saving throw against your Spell DC at the start of their turn. On a failed save, the target dies immediately, their body overcome with disease. On a success, they return to consciousness.