From publisher blurb:
Create Acid and Slime Monster Lairs in Minutes!
Enjoy quick, easy templates to spice up encounters, travel, and especially boss fights with acid and slime monsters. 5th Edition (5e) Game Masters can use them to run intense, cinematic encounters using aberrations, black dragons, or oozes, as well as any campaign featuring Cthulhu cosmic horror or body horror themes, or adventure plots that riff off classic sci-fi/horror movies like Aliens or The Thing.
In this extreme template pack, you get environment rules as well as new monsters and treasure ideas for:
Acidic Slime (magical terrain)
Slippery Slime (magical terrain)
Acid Rain (nonmagical terrain)
Acidic Vapors (nonmagical terrain)
Quickslime (nonmagical terrain, trap)
Quickslime Geyser (nonmagical terrain, trap)