5e Cards
Challenge 1/2: 1/2

Rust Monster

Medium monstrosity, unaligned

Armor Class
14 (natural armor)
Hit Points
27 (5d8+5)
Speed
40 ft.
STR
13 (+1)
DEX
12 (+1)
CON
13 (+1)
INT
2 (−4)
WIS
13 (+1)
CHA
6 (−2)
Senses
darkvision 60 ft., passive Perception 11
Languages
—
Challenge
1/2 (100 XP)
Proficiency Bonus
+2

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

Rust Metal. Any nonmagical 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. Non 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 nonmagical 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.

If the object touched is either metal armor or a metal shield being worn or carried, its 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.

How many for your party

Copies of the rust monster (100 XP each) against a party of four characters of the same level. Build mixed fights in the encounter builder.

Number of Rust Monster for each difficulty, party of four
Party levelEasyMediumHardDeadly
Level 11—23–20
Level 22—34–20
Level 323–45–67–20
Level 43–45–678–20
Level 55–78–1011–1415–20
Level 66–910–1112–1415–20

In these lists

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Questions

What CR is the Rust Monster?

The Rust Monster is challenge 1/2, worth 100 XP, with a proficiency bonus of +2.

How many hit points does the Rust Monster have?

27 hit points (5d8+5), with AC 14 from natural armor.

How many should I use against four 1st-level characters?

Against four level 1 characters, 2 is hard by the encounter XP budget.