I picked up a new level 4 spell, a frost fireball, that you can't get from natural lvl up spell selection. Are there more spells like that in the game now? Also, do we get any soulbound wizard implement? Where can I get the soulbound staff? So far I've only found the priest weapon and the estoc

The staff is in the same area as estoc - look for area with some suspiciously friendly spirits, then check around.

Thanks! Is it a good weapon for a wizard? Also, are there more "hidden" new spells, aside from the frost fireball that I should look for?

No idea who the staff will be good I'm afraid since I only just got it - gave it to Aloth all the same since no one else in my party can bind to it.