Undead Fortitude. If damage reduces the amalgamation to 0 hit points, it must make a Constitution saving throw with a DC of 5 + the damage taken, unless the damage is radiant or from a critical hit. On a success, the amalgamation drops to 1 hit point instead.

Aberrant Nature. The amalgamation counts as an aberration for any ability, trait, or other requirement where such a typing is necessary.

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

Charge. If the amalgamation moves at least 10 feet straight toward a target and then hits it with a gore attack on the same turn, the target takes an extra 9 (2d8) piercing damage. If the target is a creature, it must succeed on a DC 15 Strength saving throw or be pushed up to 10 feet away and knocked prone.

Spawn of Chaos. When the amalgamation is reduced to 50 hit points, it can make a DC 19 Constitution saving throw at the start of each of its turns. On a success, role 1d6 on the table below, with the amalgamation receives the benefit listed. If the amalgamation succeeds but has already received the rolled benefit, then this feature does nothing.

1. The amalgamation gains a flying speed of 40 ft. as it grows large leathery wings out of its back.
2. The amalgamation can make an additional two attacks per turn, on top of its normal three for a total of five attacks.
3. The amalgamation's Gore attacks now deal an additional 5 (2d4) acid damage on hit.
4. The amalgamation's walking speed increases to 60 ft. and can take the Disengage action as a bonus action.
5. The amalgamation gains the Regeneration feature, which restores 10 hit points at the start of each of its turns, unless the amalgamation has taken radiant or fire damage that round.
6. The amalgamation gains the ability to cast Dissonant Whispers twice per day, and Vicious Mockery at will, using Constitution as its spellcasting ability (Spell Save DC of 16).

Multiattack. The amalgamation makes three attacks: one Gore and two Tentacle

Tentacle. Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 9 (1d10 + 4) bludgeoning damage, plus 2 (1d4) acid damage.

Gore. Melee weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 8 (1d8 + 4) piercing damage,