Legendary Resistance (2/day). If the Ultralisk fails a saving throw, it can choose to succeed instead.

Creep Nourishment. The Ultralisk regains 24 (2d20 + 14) hit points every 1 minute if it is standing on creep and has at least 1 hit point

Responsive Creep. The Ultralisk gains 10 to its speed while on creep.

Frenzied: The Ultralisk is immune to the charmed, stunned, and unconscious conditions. Also due to it's chaotic mind, it is resistant to psychic damage, unlike the vulnerability of other zerg creatures.

Siege Monster. The Ultralisk deals double damage to objects and structures.

Torrasque Strain (Recharges after a Short or Long Rest). If the Ultralisk is killed, it enters a chrysalis state for 8 rounds, after which it regains all its hit points and becomes active again. The chrysalis has an AC of 18, 80 hit points, a damage threshold of 15. and a 10 for each stat. If the chrysalis is destroyed, the Ultralisk also dies.

Monomolecular Blades. The edges of the Kaiser blades are so sharp, they are considered magical for the purpose of overcoming resistance and immunity to nonmagical attacks and damage..

Multiattack.  The Ultralisk makes 3 attacks with its kaiser blades.

Kaiser Blades. Melee Weapon Attack: +12 to hit, reach 10 ft., 1, 2, or 3 adjacent targets. Hit: 16 (2d10 + 7) slashing damage. 

Burrow Charge (Recharge 5-6). The Ultralisk quickly burrows and charges through the earth to a point within 40 feet of it, upon where it emerges. Each creature within 5 feet of the Ultralisk when it emerges must make a DC 18 Dexterity saving throw. On a failed save the creature takes 25(5d10) bludgeoning damage and is pushed 10 feet away and knocked prone. On a successful save, the creature takes half as much damage and is pushed 20 feet away, but is not knocked prone.

The Ultralisk can take 3 legendary actions, choosing from the options below. Only one legendary action option can be used at a time and only at the end of another creature's turn. The Ultralisk regains spent legendary actions at the start of its turn.

Kaiser Blades. The Ultralisk uses it's Kaiser Blades action.

Stomp. Each creature adjacent to the Ultralisk must succeed on a DC 18 Dexterity saving throw or be knocked prone.

Tissue Assimilation (Costs 2 Actions). The Ultralisk uses it's Kaiser Blades action. It regains hit points equal to the damage dealt.