(Picture from a post on Britain in detail: quirk, charm and craft in the built environment on facebook.)
Steel Snail
A swarm of small, metallic snails that consume metals. Despite their name, their bodies usually resemble some patchy iron, but their actual composition depends on the specific metals they've been feeding on. They implacably slither towards any metal they scent, whether worn, held, or unattended.
They exude heat from small furnaces within their shells (where they digest the metals), which a whole swarm may release at once in response to danger (the equivalent to a heat metal spell applied to anyone within 10 feet of the swarm). They may do this once per day.
A swarm that inhabits an area for a long time will gradually coat surfaces in a metallic patina with their slime trails. Fanciful tales from the East have wizards feeding them diets of precious metals to gild sculptures and scrolls with unique alloys. (And providing a smokeless source of heat.)
Given their composition and behaviour, most sages ascribe their origins to one of the paraelemental planes of existence, although this has not been satisfactorily proven in the Collegia Magna and a significant minority assume them to be sorcerous constructs.
Armour Class: 5 [14]
Hit Dice: 2 to 4 (9 / 13 / 18hp)
Attacks: Special
THAC0: NA
Movement: 5’ (1’)
Saving Throws: D13 W15 P16 B17 S18 (NH)
Morale: 12
Alignment: Neutral
XP: 20 / 35 / 75
Number Appearing: 1 (1d3)
Treasure Type: Special
Size: 10’ × 10’ area, typically.
- Immunity: Unaffected by sleep spells or damage from fire. Intense cold slows them as the spell.
- Swarm attack: Anyone wearing or carrying a metal object within the swarm must make a Save vs. Petrification. If they fail, they automatically take damage — 2hp if wearing armour, 4hp without — and the snails latch onto them, doing damage automatically while still attached. This damage is magical.
- Heat Vent: Once per day, may vent heat en masse: as heat metal applied to everyone within 10 ft of the swarm.
- Consume Metals: Metals left in the swarm’s area over time will be consumed by the swarm, with small objects (e.g. thieves’ tools) consumed within 1 turn and any armour or swords consumed entirely within 1d6 hours. Magic items may save to resist as with Rust Monsters.
- Escaping: On exiting the swarm, characters continue to suffer half damage until a round is spent swatting off attached snails.
- Pursuit: Snail swarms that scent metal within 60 ft will pursue it relentlessly.
- Raw Materials: The snails’ value as metals depends on the metals they were consuming, but an “average” swarm is worth GP equal to its HP.
