Etrian Odyssey IV: Legends of the Titan 3DS

For centuries, the tree Yggdrasil has been a constant presence in the lives of the people of Tharsis. It looms on the horizon, visible from everywhere in the city. 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. The player is the latest explorer arriving in Tharsis on an adventure to seek their fame and fortune.

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.

While Prince Baldur succeeds in awakening Heavenbringer from within the ancient capital beneath Yggdrasil, he is corrupted by it. After the player strikes down Baldur, they must fight the Titan via airship. After defeating the Titan, it turns back into a tree and does not release the world-threatening toxins it absorbed, saving Tharsis from annihilation.