Incidentally, I used all of those spells that are bundled into the Hour of Power with my first party, but that was only because I had no characters capable of learning the Light & Dark magic...
Using the Prismatic Light against the Snergle's army is a cool idea... I remember dispatching the army with lots of tactical positioning, shooting arrows and casting tons of fireballs.
Dragon Breath is an awesome spell for the Castle Darkmoor, since it is a real eye-killer. One of those wipes out a whole bunch of eyes.
Cuisinarts are a good enemy type for those spells . It was hard for me to handle them with conventional weapons, but a couple of Mass Distortions and Petrifications got rid of them.
Shrapmetal works on everything, and all people here will tell you that it's the best attack spell in the game.
And I didn't get the Dark Containment either. The same for the Reanimation spell, for example.