Greater Undead Fortitude. If the Undead Monstrosity reaches 0 hit points it makes a constitution saving throw of 17. On a success the Undead Monstrosity gains hit points equal to 1d12+6.

Boil Burst. range: self(10 ft. sphere), Attack/Save: Constitution saving throw, DC: 14, Damage: 14(4d6 + 4) poison, all effected are now poisoned until the end of their next turn(the poison status effect or damage does not take effect if the target is immune).

Multi-Attack. The Undead Monstrosity takes 2 scratch attacks and 1 stomp attack.

Scratch. Melee Attack: +4 to hit, range 5 ft., 1 target, Hit: 6(2d6 + 2) slashing and 3(1d6) necrotic damage.

Stomp. Melee Attack: +5 to hit, range 5 ft., 1 target, Hit: 13(3d8 + 3) bludgeoning 4(3d4) necrotic damage, anyone with-in 5 ft. of the initial stomp must make a DC 15 Constitution Savingthrow. On a fail the target takes 4(2d4) force damge or half as much on a success.

Burrow. The Undead Monstrosity can use it's bonus action to burrow underground . To un-burrow the Undead Monstrosity uses a bonus action or action to breach the surface of the floor/ground and all creatures with-in a 1o ft. square radius must made a DC 14 Dexterity Save. On a fail the creature takes 5(2d6) bludgeoning damage or half as much on a success.