The indescribable god has awakened! —Beginning of Abyssal God's second phase, Etrian Odyssey III: The Drowned City Abyssal God is the true final boss of Etrian Odyssey III: The Drowned City. It's fought on B25F, the final floor of the Yggdrasil Labyrinth, and is arguably the hardest boss in the game. This creature is the final enemy of the explorers, the creator of the Deep Ones. No words can describe this colossal, tentacle ridden abomination. Its only visible part is its head, atop its body, with a huge, gaping maw.