I found a spell called Banosh Shadow in a D20 book. It lets you banish a shadow (the monster) to the Plane of Shadow. Similar spells would bansih demons, etc.
I'm not sure how to build the spell with the Player's Companion spell creation rules. I looked at every spell type, inluding summoning. The spell types don't include an Abjuration category, except protection, whioh doesn't seem to covefr banahing creatures. How can I build a spell that banishes a dreature on a failed save? The spell in question deals 3d4+1/level (max 10) damage even on a successful save. I'd like to include that as well, but mainly I'm looking for a way to banish creatures.