I've always been interested in planescape (and chase, the weird card based cousin) but never had a good opportunity to dive in.

Trying to narrow down ideas: how does summon magic work when going across various crystal spheres? Specifically, I've always had a soft spot for truename magic despite all its jank, and the fiend binder class from ToM removes most the worst parts and effectively gives wizard a few extra bells and whistles.

Could also go with a Goliath totemist with the goal of reaching the "highest peak" in the cosmos.