Spells that gain in power when held/charged?

[Xeolan]

Out of flavor, i was curious to know if anyone was aware of a spell or item property that gathers power, and becomes more devastating the longer it is channeled.

Ex: A modified Fireball that deals half damage if fired on first round, full damage on second, but up to 50% additional damage on third round.

And/or maybe a wand that you can consume additional charges so your spell becomes stronger.

My character uses mechanical contraptions as a backup plan to deal damage, and i was looking for something that can mimic energy being gathered in a ''plasma gun'' (or whatever legit name i'll give it later) ''à la Megaman X,'' the longer you hold it, the stronger it becomes.

Thanks =D

[Troacctid]

Sounds like you're looking for Channeled Pyroburst, from Player's Handbook II. There's also a couple other spells with similar effects, like Channeled Sound Blast from Complete Mage.

[Kraken]

I think there's also a series of feats that allow you to burn additional charges from wands when you use them in order to apply metamagic feats to them. Can't recall a source, unfortunately.

[Jack_Simth]

I think there's also a series of feats that allow you to burn additional charges from wands when you use them in order to apply metamagic feats to them. Can't recall a source, unfortunately.

It's an Artificer class feature, Metamagic spell trigger.

There's also the Double Wand Wielder feat from Complete Arcane (lets you invoke two wands a round)

There's The Rod of Many Wands, which is a rod that you load with three wands to set them all off as a full-round action (Complete Mage).

Note that there's extra charges burned for all three of those, so you'll go through money fast doing that.

[Xeolan]

Thanks guys. I really like the Channeled Pyroburst/Sound Blast spells. Exactly what i needed.

I'll also look for wands, depending on what i can actualy afford in terms of feat/gold.