Carxes, Champion of Mammon

Devil's Sight. Magic darkness doesn't impede Carxes' darkvision.

Magical Weapon. Carxes' weapon attacks are magical.

Magic Resistance. Carxes has advantage on saving throws against spells and other magical effects.

Curse of Minauros. Carxes begins combat with a curse level of 2. At the beginning of his turn he gains 2 curse levels. He gains 2 curse levels when he would take poison damage, and he gains 1 curse level when he takes acid damage. 

Brand of Minauros. When Carxes hits a creature with his claws, he may expend 3 curse levels to sear a green brand into the creature's skin. Carxes always knows the direction to the branded creature. Further, each time the branded creature deals damage to Carxes or a creature he can see within 5 feet of him, the branded creature takes psychic damage equal to Carxes' current curse level.

The brand lasts until Carxes dismisses it or until he uses this feature to apply a brand to another creature. The brand can be dispelled with dispel magic and is treated as a level 6 spell.

Accursed Resistance. If Carxes is subject to a non-magical effect or fails a saving throw, he can choose to expend 1 curse level to end the effect or automatically succeed the saving throw.

Spellcasting. Carxes' spellcasting ability is Consitution (spell save DC 17, +9 to hit with spell attacks). He can inately cast the following spells:
Cantrips (at will): mage hand, acid splash, eldritch blast
1st level (2 slots): cause fear, hex
1/day each: floating disk, arcane lock, incite greed

Multiattack. Carxes makes two claw attacks.

Claw. Melee Weapon Attack: +8 to hit, reach 5 ft., one target. Hit: 9 (2d4 + 4) slashing damage and 4 (1d8) acid damage.

Constrict. Melee Weapon Attack:  +8 to hit, reach 10 ft., one target. Hit: 11 (2d6 + 4) bludgeoning damage and 4 (1d8) acid damage, and the creature is grappled. While grappled, the creature takes 1d8 acid damage at the beginning of each of their turns, and they may use an action to attempt to break the grapple (DC 16). Carxes can only grapple one creature this way.

Hellish Geyser. Carxes expends 3 curse levels to summon a geyser of mud and acid from the swamps of Minauros. It erupts from any surface Carxes can see in a 15 foot cube. Creatures within the space when it erupts must make a DC 17 Dexterity saving throw or take 3d8 acid damage, or half as much on a successful save. At the end of Carxes' turn, the acidic mud settles on the ground in a 15 foot square directly under the geyser's area. Creatures in the space at this time, creatures that enter the space on their turn, or creatures that end their turn in the space must make a DC 17 Dexterity saving throw or take 2d8 acid damage, or half as much on a successful save. At the end of Carxes' next turn, the acid no longer deals damage and the space becomes muddy difficult terrain.

Curse of the Muddled Mind. Carxes expends 2 curse levels to curse a creature that he can see within 30 feet of him that is concentrating on a spell or using a feature that requires concentration. That creature has disadvantage on the next Constitution saving throw it makes to maintain concentration before the end of Carxes' next turn. If Carxes chooses, he takes damage equal to twice his current curse level, minimum of 1, and the creature has disadvantage on all Consitution saving throws it makes to maintain concentration before the end of Carxes' next turn.