Bone Grinder the Ancient Shade Beast

Death Burst. When bone grinder dies, he bursts into flames that are as bright as can be. Each creature within 10 feet of it must make a DC 21 Dexterity saving throw, taking 27 (6d8) fire damage plus 27 (6d8) necrotic damage on a failed save, or half as much damage on a successful one.

Faultless Tracker. Bone grander knows the direction and distance to his prey even if his prey is in another plane of existence.

Fire Absorption. Whenever bone grinder is subjected to fire damage, he takes no damage and instead regains a number of hit points equal to the fire damage dealt.

Immutable Form. Bone grinder is immune to any spell or effect that would alter his form.

Life Eater. A creature reduced to 0 hit points from damage dealt by bone grinder dies and can't be revived by any means short of a wish spell.

Magic Weapons. Bone Grinder's weapon attacks are magical.

Necrotic Absorption. Whenever bone grinder is subjected to necrotic damage, he takes no damage and instead regains a number of hit points equal to the necrotic damage dealt.

Siege Monster. Bone grinder deals double damage to objects and structures.

Multiattack. Bone grinder makes two claw attacks and one bite attack.

Bite. Melee Weapon Attack: +13 to hit, reach 5 ft., 1 target. Hit: 13 (2d6 + 6) piercing damage plus 9 (2d8) fire damage and 9 (2d8) necrotic damage.

Claw. Melee Weapon Attack: +13 to hit, reach 10 ft., 1 target. Hit: 14 (2d8 + 6) slashing damage plus 9 (2d8) fire damage and 9 (2d8) necrotic damage.

Darkness Aura (1/Day). A 20-foot radius of magical darkness extends out from bone grinder, moves with he, and spreads around corners. The darkness lasts as long as bone grinder maintains concentration, for an indefinite time (as if concentrating on a spell). Darkvision can't penetrate this darkness, and no natural light can illuminate it. If any of the darkness overlaps with an area of light created by a spell of 2nd level or lower, the spell creating the light is dispelled.

Fire Breath (Recharge 6). Bone grinder exhales a 40-foot cone of fire. Each creature in that area must make a DC 21 Dexterity saving throw, taking 27 (6d8) fire damage plus 27 (6d8) necrotic damage on a failed save, or half as much damage on a successful one.

Channel Negative Energy (Costs 1 Actions). Bone grinder magically unleashes negative energy. Creatures within 60 feet of bone grinder, including ones behind barriers and around corners, can't regain hit points until the end of bone grinder's next turn.