Odin, the Norse god of wisdom and magic, and king of the Asir, gave his eye to gain knowledge from drinking from the well of wisdom, hung himself to invent magic, and keeps the severed head of the giant Mimir conserved with herbs to ask its counsel.
The many attributes of gods are fascinating to depict; Odin here has both his ravens, the spear Gungnir that returns after being thrown, and the golden ring Dreipnir that replicates itself eightfold every nine days. Most paintings show him old and grey and focus on his missing eye, but what I always liked most about him is his unquenchable thirst for knowledge and understanding. I wanted to show that longing, making him lean forward to drink wisdom from the dying lips of a slain giant (who, being the oldest beings in the world, are also the wisest). Mimir I wanted to look somewhat inhuman, and really big, even if it's also said that Odin has the head with him at all times. I guess he'll have to use his godly strength to haul it around.