Magic Resistance. The Undead Helmed Horror has advantage on saving throws against spells and other magical effects.

Spell Immunity. Undead Helmed Horror immune to three spells chosen by its creator. Spells: Fire Ball, Heat metal and 

symbiotic relationship. The Undead Helmed Horror has fused with a Black pudding making it have a symbiotic relationship working together and hinders forced separation of the two.

Oozing aura. within 10ft of the Undead Helmed Horror will be difficult terrain 

Multiattack. Undead Helmed Horror maked an Longsword attack and a Black pudding follows up with an attack.

Longsword. Melee Weapon Attack: +9 to hit, reach 10 ft., 1 target. Hit: 14 (2d8 + 5) Slashing damage or 15 (2d10 + 4) Slashing damage (Two Handed)

Skeleton  OozeThrow. Ranged Attack: +9 to hit, reach 5 ft., one target. Hit: 7 (1d6 + 4) piercing damage plus 18 (4d8) Necrotic damage. 

Black pudding attack. Melee Weapon Attack: +9 to hit, reach 5 ft., one target. Hit: 7 (2d6 + 4) bludgeoning damage plus 18 (4d8) necrotic damage. In addition, nonmagical armor worn by the target is partly dissolved and takes a permanent and cumulative −1 penalty to the AC it offers. The armor is destroyed if the penalty reduces its AC to 10

Slide. The pudding lets the Undead Helmed Horror slide along the ground for 20ft in a straight line or diagonally but no turning.

Trail. The lower part of the Undead Helmed Horror leaves a 10ft wide trail of black ooze slowing town creatures and causing them 1 points of acid damage for every 5ft of movement used on top of the trail.