Ancient Roman: Power Of Dark Side

Young protagonist Kai is an orphan who grew up as a slave in a mining town. When a mysterious gem is found in the mines an evil dark lord arrives to claim it, and threatens to kill all the workers. Kai and his friends band together to escape, and journey out into the world. On their travels they try to discover the secret of Kai's past, have to deal with a curse that turns humans into monsters, and finally confront the evil source behind all of it.