All NINE-WORLDS lurk within its branches — and then some.
Its three roots run riot, starting from ASGARD, JOTUNHEIM and HELHEIM where they are nourished by various beneficial waters including URD’s Well of Knowledge where MIMIR lurks. Not forgetting the NORNS who reside under it.
YGGDRASIL is home to an abundance of wildlife both magical and malicious, from gnawing NIDHOGG the dragon to entire herds of nibbling goats. In fact the tree is under constant threat of global catastrophe but the Norse Gods seem powerless to act.
Dew from the YGGDRASIL supplies mead for VALHALLA, and when the world ends in almost total devastation this tree will still be there, containing seeds for the next crop of beings. Hopefully humans, but most likely more bloody ash trees. I swear one is coming up at the end of my garden where I have a constant battle to keep it at bay.