Regeneration. The Symbiotie regains 10 hit points at the start of its turn. If the Symbiotie takes fire damage, it regains only 5 hit points at the start of its next turn. The troll dies only if it is hit by an attack that deals 10 or more a fire damage. 

Symbiosis. The Symbiote takes half the damage the creature it is bonded to takes and the creature takes half the damage the Symbiote takes.

Armor Form. The Symbiote can envelope their creatures form In a slimy goo to protect them as a bonus action. Doing so gives them resistance to all damage and ignores the Symbiosis trait, while Armor Form is active  the creature is on size larger, uses the Symbiote’s strength, dexterity, and constitution unless any of the creatures scores are higher. The Symbiote can only Attack while in Armor Form

Multiattack. The Symbiotie makes three attacks: two claw attacks and one bite attack.

Razor Claws. Melee Weapon Attack: +5 to hit, reach 10ft., 1 target. Hit:  7 (2d6 ) Slashing damage. 

Crushing bite. Melee Weapon Attack: +7 to hit, reach 5 ft., 1 target. Hit: 11 (2d10) piercing damage.