Brown Slime (5e Hazard)
From D&D Wiki
A sticky brown ooze that can often be found stuck to trees or rock faces, brown slime gradually coats creatures that touch it. A creature that touches brown slime takes 4 (1d8) acid damage and is restrained, taking 4 (1d8) acid damage at the start of each of its turns until it is freed. A restrained creature or a creature within 5 feet of the restrained creature can use its action to make a DC 14 Strength (Athletics) check, breaking free on a success. If a creature remains restrained by brown slime for at least 1 minute, the slime begins to coat it, and the DC of the Strength (Athletics) check to break free increases to 16. It takes 1 minute for a Medium or smaller creature to be completely enveloped by brown slime, plus 1 minute for each size it is larger than Medium. A creature enveloped in brown slime is at risk of suffocation, and the DC of the Strength (Athletics) check to break free increases to 17. Brown slime doesn't attack other oozes, and it prefers to feed on the flesh of humanoids to ordinary animals.