Monstrous Mondays: Magiphagous Rust Monster

Rust Monsters are a great threat to low-level characters.  Nothing scares a group of fighters as much as a rust monster.  Orcs, kobolds, goblins, even trolls can be dealt with when you know what is going on.  But a rust monster never fails to put fear into most players.  Just not for the reasons the other monsters do.

Plus I have to admit I have always loved these weird little dudes. Especially after I learned of their true origins!

So here is a version of the rust Monster my oldest is using in his games.  Helps keep the fear of these guys alive, even when characters have gone up a level. Maybe even more so that they have gone up in levels.

Rust Monster, Magiphagous

Appearing as a paler and larger version of the rust monster, these creatures are otherwise exactly the same as rust monsters, save for one detail.   These creatures only eat magical metals.

Rust Monster, Magiphagous  (Old-School Essentials)
Magical, armadillo-like creatures with long tails and two long, antennae-like feelers. Feed on the remains of magical metals.
AC 2 [17], HD 7 (31hp), Att 1 × feeler (rusting), THAC0 13 [+6], MV 120’ (40’), SV D11 W12 P13 B14 S15 (5), ML 9, AL Neutral, XP 175, NA 1d4 (1d4), TT None

• Rusting: Magical metal that touches a rust monster (e.g. weapons that hit it, or armour struck by a feeler) crumbles instantly to rust.  Each time a magic item is affected, it loses one “plus”.  Each item gets a base saving throw of 13, plus any "pluses" the magical item has.
• Mundane damage immunity: Can only be harmed by magical attacks.
• Smell metal: Attracted by the scent of magical metals such as weapons, armors and artifacts.

Rust Monster, Magiphagous (Fantasy Age and Blue Rose)

Abilities (Focuses)
1 Accuracy (antennae)
–3 Communication
2 Constitution
1 Dexterity
2 Fighting (Claws)
–3 Intelligence
1 Perception (Smelling)
2 Strength
1 Willpower

Speed 14
Health 20
Defense 12
Armor Rating 4

Weapon Attack Roll Damage
Antennae +4 1d6+2

Special Qualities
Favored Stunts: Knock Prone

Eat Magic: The Magiphagous Rust Monster eats magic from metal magical items leaving behind useless rust.

Threat: Minor


and for 5e D&D

Rust Monster, Magiphagous

Large monstrosity (magical), unaligned

Armor Class

 

15 (natural armor)

Hit Points

 

52 (7d10 + 14)

Speed

 

40 ft.

STR

14 (+2)

 

DEX

12 (+1)

 

CON

14 (+2)

 

INT

2 (-4)

 

WIS

13 (+1)

 

CHA

6 (-2)

Senses

 

darkvision 60 ft., passive Perception 11

Languages

 

—

Challenge

 

1 (200 XP)

Magic Scent.

 The rust monster can pinpoint, by scent, the location of magical metal within 30 feet of it.

Rust Metal.

 Any magical weapon made of metal that hits the rust monster 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. Magical ammunition made of metal that hits the rust monster is destroyed after dealing damage.

Actions

Bite.

 Melee Weapon Attack: +3 to hit, reach 5 ft., one target. Hit: 5 (1d8 + 1) piercing damage.

Antennae.

 The rust monster corrodes a magical ferrous metal object it can see within 5 feet of it. If the object isn't being worn or carried, the touch destroys a 1-foot cube of it. If the object is being worn or carried by a creature, the creature can make a DC 11 Dexterity saving throw to avoid the rust monster's touch. Bonuses to save per plus of the item's enchantment.

If the object touched is either metal armor or a metal shield being worn or carried, it takes a permanent and cumulative -1 penalty to the AC it offers. Armor reduced to an AC of 10 or a shield that drops to a +0 bonus is destroyed. If the object touched is a held metal weapon, it rusts as described in the Rust Metal trait.