Sky-Runner

Sky-Runner is alive! It is a giant orange space squid with five tentacles, and the armoured red rig it wears is not built into it: the Light Star beam both controls the creature and clads it, adding speed and missiles. That makes it a mount rather than a machine, which matters for a catalogue that has to decide what counts as a vehicle.

One wiki records a good detail that fits the show’s own logic. While Mon*Star was in prison Sky-Runner forgot him and attacked him on his escape, until a Light Star blast restored its memory.

Kenner released it in the second wave with grasping tentacles and a launching missile.

Sources: Wikipedia, TV Tropes, thundercats.fandom, thundercats-ho.fandom, The Cartoon Databank.