Rust worm

"You mean they're acting so smart because they're so stupid?"

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

After Thunderclash had publicly announced the Wreckers' arrival on Velocitron, Aileron wondered if, among theories, the Wrecker leader had rust worms in his brain module. Tread & Circuits Part 1

"I feel I was denied critical, need-to-know information."

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 the idea End of Time of turning the Insecticons against the rust worms. The Landscape of Fear

When Pyra Magna and her Companions set out for the Sonic Canyons, they witnessed the rust worms consuming Cybertron's wilderness, something Jumpstream noted she'd not seen in her trip to the future. Given that Jumpstream was fated to die in the Canyons, Pyra ordered her to stay behind. Left in the wilderness, Jumpstream continued to observe the worms, continually teleporting away when they got too close. War's End Part Two

Following a temporary Autobot/Decepticon ceasefire, the Autobots made for Darkmount, only for Megatron to renege on the agreement. At his order, Jhiaxus began a bombing campaign that put the Autobots in the path of the rust worms. Radical Time To buy time for the fliers to continue on to Darkmount, Optimus Prime and the Prime Guard fought a delaying action against the worms. As Chromia's team regrouped with them, Novastar managed to attach Termagax's data-bomb onto Bombshell. Just as the rust worms were about to overwhelm Optimus Prime's unit, the data-bomb took effect, giving the Insecticlones the new directive to attack the rust worms, though Optimus wondered if the Insecticons were truly able to destroy them. End of Time