Rust Dragon

From a distance a rust dragon passes for a metallic dragon, but it is part insect: butterfly-shaped wings, antennae, and teeth that are jagged spurs of its exoskeleton. Its pitted, corroded-looking hide is splashed with orange, brown and dark red, and anyone who takes that corrosion for a weak point is badly mistaken. There is only one true kind, yet each individual echoes a metallic breed in tarnished form: blackened silver, stained brass, or copper gone green with verdigris.

It has every natural weapon of an ordinary dragon and the instinct to use them, but it never casts spells and gains no age-based powers. It has two breath weapons. The first is an acid jet 5 feet wide and 75 feet long, half damage on a save. The second is a cone of rust-red oxidant, 5 feet wide at the mouth, 75 feet long and 30 feet across at its end; any metal it reaches needs a save vs. disintegration or crumbles instantly into drifting rust.

Rust dragons wander the decaying iron cubes of a plane of endless war and have never been known to leave it. Solitary, they settle any meeting with a harmless shoving match that ends when one gets its mouth around its rival's head. They keep no hoards; only a great wyrm might save a few gems. What they gather is iron, steel and now and then spells, for food and defense. A faction devoted to entropy cites them as proof the cubes, and everything else, are dying, while others insist the cubes are merely becoming something new.

The sages are right that rust monsters are kin. Those insectlike beasts hatch in great swarms and fend for themselves, and the few survivors somehow find their way to the rust-cube layer of this plane. Each burrows into a remote tunnel, gorges for a year, spins a metal cocoon, and sleeps three years before bursting out as a hatchling dragon. No one knows if rust monsters are native here or are Prime creatures transformed by the plane, nor what role the dragons play.

Achaierai sometimes collect the cocoons and keep the dragons that emerge. Whether from that long watch or something else, such dragons tolerate one another and seem fond of the birds, who use them to dig tunnels in the iron cubes. What the dragons gain from the deal is unknown.