Anyone who has played through the game to the end may have noticed this spell in the game. Of course, it requires 14 points in a skill you don't get until rather late, and therefore most players don't use it.

I have used it, and have found that it is definitely worth saving the respec orb so you can get this spell. In fact, I have actually played through Hard++ with a pure mage setup (staves and potions allowed). The combination of Ghost Form potions and Reflect Projectiles makes the end game easy, as I can just skip most of the dangerous enemies.

I generally played the game the same way (Hard++), albeit I was more warrior based, and I played before the "KP" system that was implemented in a future patch. I can contend to your statement, because once I started getting alteration and protection magic, holy crap. It's absolutely worth waiting to respec. Too bad you can't respec more than once per save though, unless you use those Unepic points. :\