Gray Ooze 2014
CR 1/2 ooze
Medium ooze (Oozes), unaligned
The ooze can move through a space as narrow as 1 inch wide without squeezing.
Any nonmagical weapon made of metal that hits the ooze corrodes. After dealing damage, the weapon takes a permanent and cumulative -1 penalty to damage rolls. If its penalty drops to -5, the weapon is destroyed. Nonmagical ammunition made of metal that hits the ooze is destroyed after dealing damage. The ooze can eat through 2-inch-thick, nonmagical metal in 1 round.
While the ooze remains motionless, it is indistinguishable from an oily pool or wet rock.
Actions
Melee Weapon Attack: +3 to hit, reach 5 ft., one target. Hit: 4 (1d6 + 1) bludgeoning damage plus 7 (2d6) acid damage, and if the target is wearing nonmagical metal armor, its armor is partly corroded 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.
Environments: Caves, Mountain, Ocean, Ruins, Sewer, Plane of Earth, Underworld
Other versions
Source: System Reference Document 5.1 (Wizards of the Coast) · License: Creative Commons Attribution 4.0 / OPEN GAME LICENSE Version 1.0a details