Rust Monster

Magical, armadillo-like creatures with long tails and two long, antennae-like feelers. Feed on rusted metal.

AC2 [17], HD5 (22hp),
Att 1 × feeler (rusting), THACO 15 [+4],
MV 120’ (40’), SV D12 W13 P14 B15 S16 (3),
ML 7, AL Neutral, XP 175, NA 1d4 (1d4),

• Rusting: Metal that touches a rust monster (e.g. weapons that hit it, or armour struck by a feeler) crumbles instantly to rust. Magic items have a 10% chance per “plus”, to be unaffected on each successful hit. Each time a magic item is affected, it loses one “plus”.
• Smell metal: Attracted by the scent.

Source: Classic Fantasy