Rust worm

Rust worms are voracious, writhing creatures that inhabit the Sea of Rust. They feast on metal and any Transformer unfortunate enough to enter their domain will quickly find themselves entangled and devoured.

Fiction

2019 IDW continuity

Though a mythological account held that the Great Rust Sea formed from the nucleon of Primus himself, I Have No Mouth And I Must Starscream the Sea of Rust began with the rust worms. During Cybertron's Age of Expansion, the worms discovered the metal planet and began feasting on its innards, secreting liquid rust as they consumed. When the greatest minds on Cybertron failed to contain the animals, the planet did so itself, forming an impenetrable basin that halted the worms, creating the Sea of Rust. Sea of Rust I

When unusually intense tectonic activity began plaguing Cybertron, Geomotus worried that the quakes could fracture the sea's impermeable layer and release its rust worms into the planet's crust. Escape Part Two

When the Decepticons brought down the Titans, Citadel landed in the Sea, Titans the rust worms eagerly feasting on his remains, becoming unusually active as a result of their feast. Sea of Rust I

A later planetary tremor caused the Sea's impermeable layer to rupture, the Sea expanding to swallow Skytread and the Enigma of Combination. The worms eagerly began devouring the Decepticon, Sixshot firing on those who tried to climb out. Though Termagax was quite confident that the worms would be unable to destroy the Enigma, the Autobots were keenly aware that the existential threat posed by the worms' freedom eclipsed the Decepticon expansion. Enigmatic

As the rust worms spread further out beyond the Sea, one was overpowered and carried off by an Insecticlone giving Termagax an idea on how to stop the Insecticons. The Landscape of Fear