Fantasy Tree

A Fantasy Tree (空想樹) is a mysterious tree-like construct which sustains a Lostbelt.

Description
Originating from the Alien God, the Fantasy Trees appear to be integral to the Lostbelts. They contribute to the Lostbelts overwriting the Greater History of Man, a phenomenon called the Filtering Alternate History Phenomenon. If the Fantasy Tree of a Lostbelt is destroyed, the Lostbelt itself crumbles as well.

Destroying the Trees is apparently very difficult. Though the first was destroyed by the Priestess of the Alien God, Chaldea was able to destroy the second one only thanks to Sutr consumed a part of it, weakening it. Under normal circumstances, Chaldea would not have been able to destroy the Fantasy Tree alone.

As the Fantasy Trees mature, they are able to expel the "Seeds of Fantasy" which appear akin to alien monsters.

Orochi
Orochi was the Fantasy Tree of the Russian Lostbelt.

Sombrero
Sombrero was the Fantasy Tree of the Norse Lostbelt.