Etrian Odyssey IV: Legends of the Titan[2] is a dungeon crawler role playing video game developed and published by Atlus for the Nintendo 3DS.

But its roots are in a far-off land where no one has ventured until the Outland Count of Tharsis sponsors an Explorers Guild to reach Yggdrasil and discover its secrets.

After venturing through numerous lands, the player discovers a sealed-off, fallen Empire with more advanced technology whose prince, Baldur, wishes to awaken the Titan, also known as Heavenbringer, the humanoid form of Yggdrasil.

The tree itself, along with the other "servitor" races besides humans, were bioengineered by an ancient civilization to purify the land after an unknown calamity, but they perished before they could finish the project, causing it to eventually go berserk.

An optional post-game dungeon is the Hall of Darkness, a facility in which ancient researchers attempted to develop a countermeasure to Yggdrasil should they lose control of it, but failed and created an even more powerful abomination that they were forced to seal away.

Also, dragons periodically roam the overworld, and will instantly knock out the entire party if the player's airship comes within their attack range, usually, but not always, causing a game over.