War of Humans and Monsters

The War of Humans and Monsters was a legendary clash between humans and monsters, taking place years before any human fell into the Underground.

Overview
Humans and monsters were said to have, before the war, ruled Earth in harmony.

Aftermath
After the humans claimed their victory, they concluded the war by sealing all of Monsterkind beneath Mount Ebott with a magic spell. According to many resources, it was a very long battle.