[It houses yggdrasil Tree which is stated to be immense and central sacred tree. It is fully healthy sapling that have a spirit of the yggdrasil and its servants dwelling in it. It comes from the original yggdrasil Tree that have 9 leaves which houses 9 realms such as
Asgard, Álfheimr/Ljósálfheimr, Vanaheim, Niðavellir/Svartálfaheimr, Midgard (Earth), Jötunheimr/Útgarðr, Niflheim, Helheim, and Múspellsheim. As it is getting destroyed by
Níðhöggr it uses all it's power to find the worthy, strong individual. It finds the user and gave him it's sapling, it will fully grow in 30 years. Yggdrasil tree/saplings have it's own magic/power system. Once it is fully grown any one of the leafs is a world, world item, can be used as crafting material, create world items etc... It is fully loyal to the user as it is its protector. User can use the tree to gain knowledge and the knowledge of worlds that reside in yggdrasil. For others they have to sacrifice anything that have a bond to them, higher the sacrifice valve the higher the knowledge they grain. It's an equivalent exchange.
It can even empowered and strengthen the base of the user. It in a secret hidden room where no intruder have any chance to enter the room, It highly enchanted, Have a guardian.]