Level. Nothing else. Pie increases Spell Points and Stamina. I usually ignore it until after Reflextion--and Powercast if i want it--and a decent Vit/Str is built for a Hybrid.

one thing ive noticed while casting spells for practice is the following.

To increase points in that particular realm, cast spells in the green or level 1.

To raise your divinity/alchemy/psionic/wizardry, it seems to increase quicker if you try casting the spell with the colour being yelow orange or red.

specially once your kill levels have gone past 75.
after 90 u need a crapload of spell scast on level7 to get anywhere.

Thanks PooBaa, I read that somewhere else for training realm vs. Book skills. But after seeing another confimation on that I'm going to give it a try.

i disagree with piety because in one of my current partys my priest had 100 pie but no fire skill and could still cast light at PL 1 in green

Elemental shield is a level 4 spell. Hybrids can learn it at level 12.

I started about eight 4-hybrid parties. 3 of them survived.