A crossover with the MobA strategy game DotA 2 by Valve Software.

"Since the two spirits of ancients escaped from the mad moon and begun calling for heroes to represent them in the gruesome fields of petty conflict with one-another, not a single calling or heroes has gone amiss. Until now, that is. A spell that would bring alleged heroes from another realm is detected by one of it's deities, who feebly attempts to stop it's channeling. Unfortunately for those involved, this makes the spell become more like that of a Rift between realms, and the casters are usually pulled in to sed vortex. This is on of those cases.
At least, that's what I can gather from these old tomes, and what one of our new... 'Friends' have told us."
~Twilight S.

Update- edited description to the new direction of the story.