I assume the most of you are familiar with the mythology of the Yggdrasil, but I am going to summarize it here just to explain what you see in the drawing. Yggdrasil is the great cosmic ash, three roots support it. Near one of these roots, the residence of the Norns can be found. They are in charge of mankind's destiny and they tend to the giant tree. You can see them here, kind of oversized, as spiritual superhuman entities should be, pouring water from a sacred spring.
Raskator, the squirrel runs up and down the trunk of the tree reporting the angry exchanges of the eagle that leaves on the top branches and the demonic snake that coils at the roots. Four stags also live in the branches and eat the leaves of the Yggdrasil. In the drawing the stags have become part of the tree...you can see just three of them because the fourth is roaming on the other side! ;)
Yggdrasil is the source of cosmic wisdom and that's to acquire such wisdom that. Odin chose to spend nine nights without food or water hanging from its branches. Here he has joined the stags and surveys the universe from the foliage....
Finally, Yggdrasil is considered the only tree capable of surviving the Twilight of the Gods. After the apocalypse, when a new hearth, sky and sun will be generated and life will start over fresh and renovated, from the wooden depths of the tree, two new human beings, Lif and Lifthrasir, will rise. They will eat exclusively morning dew and will be the progenitors of the new human kind.
I guess that covers it all! Enjoy!