Odin is specifically listed as being a 20th level LLW, Diabolist, Summoner, Temporal Wizard, and Necromancer, It is stated that he gained all of these from the World Tree, but then, under magic knowledge the book says:
Knows ALL spell magic of all levels, including spells of legend, temporal magic, circles, wards and rune magic (which he never shares). He also knows all Necromantic spells described in Rifts Africa, but does not have a Necromancer's special powers and tries to avoid using this dark magic.
So, he specifically didn't get the Necromancer O.C.C. abilities, but did get Diabolist and Summoner abilities?
How have you handled this in your games?