Aranleif

Aranleif the Ultimate (焉龍(えんりゅう)アランレイヴ, Enryuu Aranreivu) was one of the three Rulers of Dragonia. He died, along with his seven followers, in a battle against 3,496 Ex-Machina. His Far Cry diverted under Schwi's suggestion is what resulted in the destruction of Riku's village.

Considering the fact that Ex-Machina would not attack other races unprovoked, it's probably Aranleif's party that started the fight.