History
The Anti-Tree, said to be Yggdrasill's shadow, was located in the Hades.[1] When the Olympians died and were reborn,[2] they left the Hades itself behind, causing it to be broken, half-transformed, half-dead and rotting, same as Pluto himself. Due to this, the Anti-Tree was hanging in the vermillion sky oozing bile and dark wisdom.[1]
When Valkyrie traveled to Hades on her mission to escort Heimdall's soul to the Far Shore, they were attacked by the corrupted Pluto and his demons. They both entered the hole of the Anti-Tree, the abyss, which attacked them mentally with wounds and traumas from their past before escaping the realm.[1]