Amorphous. The Grease Jelly can move through a space as narrow as 1 inch wide without squeezing.

Innate Spellcasting(5/day). The Grease Jelly can innately cast Grease without any components.  

Melt. If the Grease jelly takes Fire damage it liquefies into boiling grease and its attacks do an extra 6 (2d4)  Fire damage. The Grease Jelly returns to its original form into rounds. 

Spider Climb. The Grease Jelly can climb difficult surfaces, including upside down on ceilings, without needing to make an ability check.

Pseudopod. Melee Weapon Attack: +4 to hit, reach 5 ft., 1 target. Hit: 11 (2d6 + 4) Bludgeoning damage plus 6 (2d4) Acid damage.

Split. When a jelly that is Medium or larger is subjected to Lightning or Slashing damage, it splits into two new jellies if it has at least 20 hit points. Each new jelly has hit points equal to half the original jelly's, rounded down. New jellies are one size smaller than the original jelly.