Elf Tree

Elf Trees are trees used by elves for habitation and architecture.

Background
Elf trees were developed in the Elf Country in response to the various dangerous monsters that inhabited the Great Forest of Evasha. The ground floor of the forest being dangerous for living forced the elves to move to the treetops.

The trees form a central part of elven culture. Elf trees are a variant of trees that are created through the magic of elven druids. Elven druids use their magic to grow and transform trees for habitation and architecture by creating cavities inside for housing. The trees are connected via simple suspension bridges which aggregately form an elf village. According to Ainz Ooal Gown, this was a type of magic that did not exist in YGGDRASIL. This tree altering magic is apparently only exclusive to elves and only they can use their magic on elf trees.

The Half Elf God-kin Arc
and The Half Elf God-kin II Arc Ainz Ooal Gown gain knowledge of elven culture, from the Elven Slaves and was particularly interested in the elf trees.

Trivia

 * The Gigantic Tree was assumed to be a type of variant elf tree, by the Elven Slaves.