Devilstar

The Mecha Planet is a planet from the Generation 1 continuity family.

The Mecha Planet (メカ惑星 Meka Wauksei) is an offensive weapon used by the Decepticons.

Fiction

Transformers (Mystery of Convoy)

Ultra Magnus confronted the Mecha Planet, which attacked with Kabses. Avoiding them, Ultra Magnus transformed into vehicle mode, positioned himself underneath the Planet, and shot it, defeating the Planet.

Ultra Magnus would later confront the very similar Twin Planets. Use Trailer Mode to Defeat the Mecha Planet!