[Theory] Ancient Demacia was a VERY magically potent place - why Galio comes alive.

Incoherent mess below

I believe that Ancient Demacia (i.e. Demacia well before any Demacians actually settled there) was one of the most magically potent regions in all of Runeterra - somewhere between Ionia and The Blessed Isles as a frame of reference. I believe that it was basically an Elderwood full of Sprites and Treants and other such guardians of nature - generally brimming with magic.

As isolated as Demacia was - hidden by a maze of mountainranges - it could not remain untouched by the Rune Wars. And, one day, it was devastated by a World Rune - essentially freeze-drying the land. All magic was sucked from the land within minutes - leaving behind an eerie dead landscape completely devoid of magic.

What remained, however, was a petrified forest that longed for magic to return to the land and breath life back into it.

Excerpt from Galio's Lore

In the aftermath of the Rune Wars ... refugees across the lands fled from the destructive power of magic. Some say that in the west of Valoran, a band of these displaced people were pursued by a vicious band of dark mages. Exhausted from days without rest, the refugees hid among the shadows of an ancient, petrified forest. The sorcerers that pursued them suddenly found their magic to be ineffective in the strange woods.

We all know what happened from here. Instead of a potent source of magic bringing the forest back to life, the refugees who settled in what would later be known as Demacia ground up the petrified trees, and turned them into stone which they used to build their defenses.

This would explain why Galio comes to life after absorbing enough magic.