Mmmm. Try some of this mithral!
  — A conversation between two rust dragons.[1]

Rust dragons were planar dragons native to Acheron that had an insatiable hunger for metal.[2]


Physically, rust dragons resembled different metallic dragons from the Prime Material plane, such as silver, copper, and brass, except that their scales seemed to be covered by different forms of oxidation and their wings were thin with an iridescent character. Those differences were only in their appearance, as all rust dragons usually possessed a similar set of strengths and abilities.[2] Moreover, rust dragons had somewhat insectoid traits, such as antennae and wings shaped in the resemblance of a butterfly's. Rust dragons' teeth were also unusual in the sense that they protruded from the creature's exoskeleton, instead of its skull.[1]

The main sources of sustenance for rust dragons were ores and metals. They had a particular liking for adamantine, gold, mithral, iron, silver, and steel, but did not turn down other metals. They also enjoyed eating meat, particularly vermin, as palate cleansers between servings of different metals, in order to better appreciate their subtle differences in taste.[2]


Unlike pyroclastic dragons or howling dragons, rust dragons were not exceedingly aggressive or violent. They mainly attacked out of hunger, and even so only to the point where they could secure sustenance. Despite being very focused on the task at hand and not tolerant of much meddling in their affairs, they were not above withdrawing from a hostile situation in which they had the disadvantage.[2]

Another trait that set rust dragons aside from other dragons was that they did not have the habit of hoarding treasure, save for a handful of gems that some of the oldest rust dragons might want to carry.[1]


Any metal object that came in touch with a rust dragon's skin or its bite immediately rusted away into uselessness. They were also incredibly resilient against damage from weapons made of metal. Only extremely powerful magic weapons had a better chance of withstanding this rusting effect, but no weapon was completely immune.[2]

Rust dragons possessed two breath weapons: a line of acid and a cone of extremely corrosive reddish-brown liquid that immediately destroyed any metal items that it touched. Only objects with some sort of magical enhancement could stand a chance of surviving it. They could also create effects similar to the acid fog, repel metal or stone, and wall of iron spells.[2][1]


Monster Manual 5e - Rust Monster - p262

A rust monster, considered by some sages to be the larval form of a rust dragon.

A minority of sages speculated that rust dragons might be related to rust monsters, but those claims were generally discredited.[2] The extremely few rust monsters who survived to reach old age somehow transported themselves to Acheron, where they ravenously consumed the abundant metal from the cubes of the plane for about one year. Afterwards, they encased themselves in cocoons made of spun metal, where they stayed for three years. Following this period, they emerged from their cocoons as rust dragon wyrmlings.[1]

It was not known, however, whether rust monsters were native to Acheron and only traveled to the Prime Material plane as a part of their larval cycle to become rust dragons, or if rust monsters were in fact native to the Prime and were altered by the magic of Acheron once transported there. In any case, it was speculated that rust dragons were largely responsible for the ongoing degradation of the oldest cubes of Acheron. The Doomguard in particular maintained that, if left unchecked, rust dragons were capable of destroying the entire plane within one millennium.[1]


Besides their home plane of Acheron, rust dragons could also be found in Banehold, Clangor, Dragon Eyrie, Hammergrim, and Nishrek.[3] If found in the Material plane, they tended to build their lair in underground caverns near veins of metal, to the usual dismay of miners. They were usually found alone,[1] but could also form families as they raised their young. Clutches of young rust dragons were also commonly found.[2]

Sometimes the achaierai collected rust dragon cocoons and raised them as pets. Domesticated rust dragons were considerably more docile and tolerant of others than their wild counterparts.[1]