unstoppable fat stalker

Invisibility. The stalker is invisible.

Faultless Tracker. The stalker is given a quarry by its summoner. The stalker knows the direction and distance to its quarry as long as the two of them are on the same plane of existence. The stalker also knows the location of its summoner.

shapechanger. The creature shapechanges into a flying snake (fly 1000ft), a giant spider (climb 70ft) black pudding

Multiattack. The stalker makes two slam attacks.

Slam. Melee Weapon Attack: +6 to hit, reach 5 ft., one target. Hit: 10 (2d6 + 3) bludgeoning damage.

Swallow. The creature attempts to swallow the player/creature attack 42+ bludgeoning damage, the player/creature must make a 2d6 dexterity saving throw if failed the player/creature is petrified. 

Elemental breath (costs 2 actions).  the creature breaths out fire, acid, air and frost the player/creature must make a 2d6 dexterity saving throw if failed the player/creature takes 20+ acid damage, 20+ fire damage, 2+ knockback damage, 10+ frost damage.