Spellcasting. Cofax Delirium is a 8th-level spellcaster. His spellcasting ability is Charisma (spell save DC 18, +10 to hit with spell attacks). He regains his expended spell slots when he finishes a short or long rest. He knows the following warlock spells:

Cantrips (at will): chill touch, eldritch blast, mage hand, minor illusion, shocking grasp

1st–5th level (3 5th-level slots): armor of Agathys, arms of Hadar, blight, hunger of hadar, contact other plane, detect thoughts, dimension door, dissonant whispers, telekinesis, vampiric touch

Pact Magic. Cofax can cast the following spells once per day, without expending material components:

circle of death, crown of stars, maddening darkness

Dagger + 2. Melee or Ranged Weapon Attack: +8 to hit, reach 5 ft. or range 20/60 ft., one target. Hit: 4 (1d4 + 3) piercing damage.

Abyssal Concepts. Each creature with at least an intelligence of 4 within 20 feet of Cofax Delirium must make a DC 18 Wisdom saving throw, as Delirium telepathically broadcasts the will and thoughts of his patron. Creatures that fail the save take 8d8 psychic damage and gain one stack of Long Term Madness, determined at random. Creatures that succeed take half damage, and instead gain one stack of Short Term Madness.