Brother Morax

For each Brittle Spine a creature has, the creature takes 3 (1d6) Poison damage at the start of each of their turns, and when Morax activates Burrow or Deep Burrow. Spines can only be removed by a Regeneration spell or similar, or by killing Morax.

Magical darkness doesn't impede Morax's darkvision.

Morax has advantage on saving throws against spells and other magical effects.

Whenever Morax is hit with a melee attack, the attacker takes 7 (2d6) Piercing damage and gains 1 Brittle Spine.

If Morax is reduced to 0 hit points while Brother Adramalech still lives, Morax regenerates 50 hit points at the start of his next turn. This regeneration is interrupted if Brother Adramalech is reduced to 0 hit points before the start of Morax's turn.

Morax makes four attacks using his Claw, Spine Fling, or a combination of the two.

Melee Weapon Attack +14 to hit, reach 10 ft., one target. 17 (3d6 + 7) Slashing damage, and the target gains 1 Brittle Spine.

Ranged Weapon Attack +13 to hit, range 30/60 ft., one target. 12 (1d12 + 6) Piercing damage, and the target gains 1 Brittle Spine.

Morax immediately deals Brittle Spine ongoing damage to all creatures that have at least one Brittle Spine that he can see.

Morax shoves an arm into the ground, rapidly growing bones that erupt at a point he can see within 100 feet of him. Each creature in a 60-foot-radius sphere centered on that point must make a DC 21 Dexterity saving throw, taking 28 (8d6) Piercing damage on a failed save, or half as much damage on a successful one. Creatures that fail the save gain 2 Brittle Spines, while creatures that succeed only gain 1 Brittle Spine.

Morax makes a Claw attack.

Morax gestures at a creature he can see that has at least 1 Brittle Spine. That creature must succeed on a DC 21 Constitution saving throw or the number of Brittle Spines it has doubles.

Morax bristles the spines within a creature that he can see. The target immediately takes Brittle Spine ongoing damage.