A monster I scribbled up over lunch yesterday and dropped (literally) on my players last night.
No. Appearing: 1
Hit Dice: 6
Armor Class: 8
No. Attacks: -
Special Attacks: Rust, surprise on 1-4
Special Defenses: Hasted by fire
Magic Resistance: 15%
Psionic Ability: Nil
Treasure Type: nil
The rust ooze is nearly impossible to distinguish from a large patch of rust. (Only a 10% chance when directly observed) They surprise opponents on a 1-4, usually dropping off of a ceiling or wall or attacking from the floor. They attack by engulfing their prey (up to 3 man sized creatures at once) Rust oozes dissolve all readied metal weapons in one round. After two rounds, they dissolve the target's metal armor and shield. After that, they dissolve any other metal objects that are not completely sealed in a pack or bag. The rust ooze causes no actual harm to bare skin, nor to any non-metal creatures or objects. Metal creatures such as robots or iron golems take 8d6 damage each turn they are in contact with a rust ooze, and tend to be singled out by the creatures in favor of hand held weapons or armor. Note that "duralloy" or similar futuristic metal is entitled to a saving throw each round.
If slain, the rust ooze dissolves into a brownish, foul smelling protoplasm that causes no futher damage to any material.
A rust ooze can choose not to dissolve metal that it is in contact with. Typically this is done to hang from an advantageous hiding place. Rust oozes can sense metal within 60 feet.
Damage from fire causes the rust ooze to be hasted, as the magic-user spell, for 1d4 rounds.
There have been reports of giant rust oozes or psionic rust oozes, but these are drunken ramblings of vagrants and braggarts, not to be trusted by wiser folk.
The party lost a scimitar, two laser rifles and a laser pistol to the creature.