Rituals, Deals with the Devil, and other short cuts to power!?

[Starbuck_II]

If you want power, you could get a wish spell by saying Pazuzu three times. You turn one step closer to CE.
He has a spell-like version of Wish: so no Exp penalty. Meaning you can wish for a created magic item without issue (magic items are created by Exp not gold cost).
But DM might add limitations even though Pazuzu has none listed.

A Metamagic rod of Greater Quicken isn't a bad choice. It would mean any spell can be used as swift action 3/day.

 

[Madeiner]

Have him make a pact. During the fight with that enemy, and only that fight, he shall gain great power (give him for example, unlimited spontaneous 8th level slots of sor/wiz spells).
His alignment however changes to evil, and the soul of the destroyed enemy will seek to destroy him out while vulnerable at the first opportunity. Invent other downsides. Maybe anthipaty cast on him for 1 week after the power is unleashed, or other things. Even better, the soul of the deceased antagonist will be compelled to cause him great pain by killing his family or friends. One of the ways to escape this fate should be ANOTHER pact with the devils. This time requiring his soul.

 

[RUMBLETiGER]

Mother Cyst feat from Libris Mortis