Ohmu magic resistance. Ohmu has advantage on saving trows against magical effects and if his master is within 5ft the master also has magic resistance.

Ohmu adamtine skin. Ohmu reduces incoming damage from atacks up to 4 y the atack is piercing, slashing or bludgeoning, if the atack is from other source of damage it only reduces it up to 2, if his master is within 5ft the master also has this ability but the damage reduction is reduced in half. 

Ohmu's eternal love. Ohmu has a master who he chooses only once in his life, he knows exactly where his master is at all times, even on different planes, has a telepathic connection with him and ha can activate some habilities, features and extend some features his master if certain conditions are meet.

Tunneler. Ohmu can burrow trough solid terrain at half his burrowing speed, he leaves a 5ft diameter tunnel.

Ohmu's rage. When Ohmus master reaches half of his maximun hp Ohmu will be mildly enraged and if his mater reaches 0hp or dies Ohmu becomes berserker and atacks everyone near him and won't stop untill his master is back on his feets or Ohmu reaches 0hp, whie in berserker mode Ohmu damage is increased, his speed is doubled and is immune to being charmed and frightened.

Berserker ram (only while berserker). Ohmu uses his body and stomps/pushes every creature on his way, when he moves all creatures/structures on his way must make a dexterity/strenght saving trow DC 20, if they fail they will suffer 14 (4d6) bludgeoning damage, if they pass they suffer half, either way they are pushed out of the way, structures suffer double the damage.

Ohmu friendly appendix (cannot use it while berserk). Ohmu channels his good will and love for his master trought his appendix giving to his master (aslong that they are within 40ft) 17 (2d8+8) of healing, if the healing excedds the master max hp then it is stored as temporal hp, it also ends condition of his choosing, against creatures that are not his master it only heals half.

 Appendix. Ohmu makes a melee natural atack againts a target, 30ft range, +8 to hit, 8 (1d8+4) bludgeoning damage and the target is moved 10ft in a direction the ohmu decides.

A thousand maws (only while midly enraged or berserker). Ohmu uses his hideous mouth full of teeths and attemps to chew on the enemie or enemies that atacked his master, the atack has 5 feet range and the target must make a dexterity saving trow DC 15 or suffer 22 (5d8) piercing damage and be restrained, they recieve 22 (5d8) piercing at the start of Ohmu turns, they can repeat the saving trow at the end of each turn, Ohmu cannot hold a gargantuan creature this way but can damage them, and can only hold one huge creature this way, while in berserker mode the objetives have disadvantage on the saving trow and the damage is increased up to 45 (10d8).

Ice fury . Ohmu exhales an icy blast in a 30-foot cone. Each creature in that area must make a DC 15 Constitution saving throw, taking 13 (3d8) cold damage on a failed save and for 1 minute affected creatures must use 1 extra feet per feet of movement, they recieve half as much damage on a successful one and are not slowed.