From the Flesh and Stone story:
If one believed the legends, he had even come to life at times, when enough mystical power had seeped into his mortar.
It's been a looong time since Galio last awakened. And we don't even know if his color story describes the last time he moved or an even earlier instance.
The beast used by the Freljordians is not described in a lot of detail, but you can get a hunch of how it looks like.
a titanic shape, seeming almost as tall as the hills behind it. It moved ominously, heaving like the waves of a troubled sea, waiting to be unleashed.
A towering behemoth of a creature – covered in thick, matted fur.
The barbarians pulled off the behemoth’s covering, revealing a snarling, mangled snout beneath a beady pair of jet-black eyes.
slaying a dozen Demacians with just one swipe of a saber-like claw.
The behemoth slammed into Galio’s mid-section with its shoulder, and let out a groan of intense pain as it crumpled to the ground clutching its collarbone.