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Rust Monster

Also known as: Corroder, Corrosion Beast

Strange monster built like a huge turtle with insectoid head and feather-like antennae

aberration metal-eater magical creature neutral subterranean

Basic Fantasy Role-Playing Game

BFRPG

Armor Class18
Hit Dice5*
Number Appearing1d4
Attacks1 touch
Damagespecial
Movement40'
Save AsFighter: 5
Morale7
XP405
Treasure TypeNone

A rust monster (sometimes known as a corroder or corrosion beast) is a strange monster built like a huge turtle, with an insectoid head sporting large feather-like antennae and a thick tail with a hammer-like protrusion at the tip which seems to serve no purpose whatsoever.

The touch of any part of a rust monster’s body oxidizes metal objects instantly, turning them to rust, verdigris, or other oxides as appropriate. One attacks with its antennae, brushing them over metal items. Non- magical metal attacked by a rust monster, or that touches the monster (such as a sword used to attack it), is instantly ruined. A hit with a non-magical metal weapon inflicts half damage before the weapon is destroyed. Magic weapons or armor permanently lose one “plus” each time they make contact with the monster.

The metal oxides created by this monster are its food; a substantial amount of metal dropped in its path may cause it to cease pursuit of metal-armored characters. Use a morale check to determine this. Metals that do not normally oxidize, such as gold, are of no interest to a rust monster and will be ignored. While rust monsters will consume oxides of silver or copper, they have a strong preference for ferrous metals (iron or steel), preferring them over any other metal.

Whether the rust monster is in any way related to the rarer ironbane (as found on page 115) is unknown, but both monsters seem to have the exact same power.

Special Abilities

Metal Oxidation: The touch of any part of a rust monster’s body oxidizes metal objects instantly. Non-magical metal is instantly ruined. A hit with a non-magical metal weapon inflicts half damage before the weapon is destroyed. Magic weapons or armor permanently lose one ‘plus’ each time they make contact with the monster.
Metal Preference: Metals that do not normally oxidize, such as gold, are ignored. Strong preference for ferrous metals (iron or steel) over silver or copper oxides.
Copyright 2006-2023 Chris Gonnerman. Creative Commons Attribution-ShareAlike 4.0 International (CC BY-SA 4.0). License

Other Sources

Old-School Essentials Classic Fantasy
Armor Class2 [17]
Hit Dice5 (22hp)
Number Appearing1d4 (1d4)
Attacks1 × feeler (rusting)
THAC015 [+4]
Movement120' (40')
Saving ThrowsD12 W13 P14 B15 S16 (3)
Morale7
AlignmentNeutral
XP175
Treasure TypeNone
Magical, armadillo-like creatures with long tails and two long, antennae-like feelers. Feed on rusted metal.

Special Abilities

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.
Copyright 2017-2019 Gavin Norman. Open Game License v1.0a. License
OSRIC
Armor Class2
Hit Dice5
Number Encountered1d2
Attacks2
DamageNil
Move180-ft
AlignmentNeutral
IntelligenceAnimal
XP3/185+4 per hp
SizeMedium (5-ft long)
FrequencyUncommon
Lair10%

Rust monsters are creatures vaguely resembling a 5-ft long and 3-ft tall giant bug-like armadillo that weighs about 200 lbs. Rust monsters have rust-red colouration on their dorsal hides, yellowish tan on their ventral hides, and two prehensile antennae on their heads.

Rust monsters are only found in underground type environments, which they prowl constantly in search of food.

Rust monsters consume metal of any kind, especially ferrous metals and ferrous metal alloys. The antennae of a rust monster can “smell” metal 90-ft away, and the creature will dart toward such a source of food with blinding speed, rolling 2 attacks with its antennae at the largest piece of metal it can sense. A successful attack causes up to 10 cubic-ft of metal instantly to crumble into easily-digestible rust and the creature will immediately cease attacking in such a case and begin devouring its newly-created meal. Metal with magical bonuses gains a 10% chance per plus of not being affected by the rust monsters attack. For instance a +3 shield would have a 30% of resisting the rusting effect. A successful “to hit” roll against a rust monster with a metal weapon automatically subjects that weapon to a rust attack.

Rust monsters are motivated by animal intelligence and blind hunger, therefore can be easily distracted from pursuit by dropping metal objects and fleeing; some iron spikes or a heavy mace will cause the attacking rust monster to stop for 1 round to devour the treat. Otherwise, rust monsters will relentlessly pursue the PCs until slain or all metal items have been consumed.

Special Abilities

Metal Detection: The antennae of a rust monster can “smell” metal 90-ft away.
Rusting Attack: A successful attack causes up to 10 cubic-ft of metal instantly to crumble into easily-digestible rust. Metal with magical bonuses gains a 10% chance per plus of not being affected by the rust monsters attack. For instance a +3 shield would have a 30% of resisting the rusting effect. A successful “to hit” roll against a rust monster with a metal weapon automatically subjects that weapon to a rust attack.
Distraction: Can be easily distracted from pursuit by dropping metal objects and fleeing; some iron spikes or a heavy mace will cause the attacking rust monster to stop for 1 round to devour the treat.