Age of Titans

Roughly 500 million years ago until 100 million years ago
Titans, one of the most mighty of the Gods creations, gather armies of giants and battle the other mighty races, such as dragons, for supremacy of Terrus. They are mostly successful.

Many of the 'lesser' beings are enslaved during this time.

The Age and virtual stalemate come to an end when some catasrophe occurs and rips a hole into the planes.