Armor Class 21 (natural armor)
Hit Points 337 (25d10 + 200)
Speed 40 ft.
Saving Throws STR +14, DEX +13, CON +15
Skills Acrobatics +20, Athletics +21, Intimidation +11, Medicine +10, Stealth +13, Survival +10
Damage Resistances cold, [object Object]
Damage Immunities fire, poison
Condition Immunities poisoned
Senses darkvision 120 ft., passive Perception 13
Languages Celestial, Common, Draconic, Infernal, telepathy 120 ft.
Challenge 21
Brittle Spine. 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.
Devil's Sight. Magical darkness doesn't impede Morax's darkvision.
Magic Resistance. Morax has advantage on saving throws against spells and other magical effects.
Spined Hide. Whenever Morax is hit with a melee attack, the attacker takes 7 (2d6) piercing damage and gains 1 Brittle Spine.
Unbreakable Bond. 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.
Multiattack. Morax makes four attacks using his Claw, Spine Fling, or a combination of the two.
Claw. Melee Weapon Attack: +14 to hit, reach 10 ft., one target. Hit: 17 (3d6 + 7) slashing damage, and the target gains 1 Brittle Spine.
Spine Fling. Ranged Weapon Attack: +13 to hit, range 30/60 ft., one target. Hit: 12 (1d12 + 6) piercing damage, and the target gains 1 Brittle Spine.
Deep Burrow. Morax immediately deals Brittle Spine ongoing damage to all creatures that have at least one Brittle Spine that he can see.
Bone Spikes (Recharge 5–6). 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.
Claw. Morax makes a Claw attack.
Bone Splinters (Costs 2 Actions). 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.
Burrow (Costs 2 Actions). Morax bristles the spines within a creature that he can see. The target immediately takes Brittle Spine ongoing damage.
CoA, p. 186