Any ways to change the school of a spell you're casting?

[Black_Zawisza]

My DM has given me a magic item that, for every round I spend casting a spell, allows me to increase its caster level by 1, 3, 6, and finally 10 (after 4 rounds). Only problem is, it only works on Evocation spells (it's meant to model Samus Aran's charged shots). Is there any way to cast a non-Evocation spell as an Evocation?

[Nettlekid]

The only instance I've ever seen of a spell changing schools wouldn't help you, I'm afraid. The only one I've ever seen was a Transmuter Wizard from UA, which allows you to change the school of one spell to Transmutation, which means you can add even a banned spell to your list. But that's not useful for your Evocation thing.

What kind of spells do you want to add to it? Maybe the DM would allow you to use Orb of Fire, Orb of Cold, Orb of Electricity, and Orb of Force to imitate the Plasma Beam, Ice Beam, Wave Beam, and Power Beam. I mean, they're Orbs, which is very Samusy.

[Kornaki]

Separately, I can't imagine your DM will be very amused if you start using his "charge up your shot" item to extend the duration of invisibility

[GoodbyeSoberDay]

I can't help on the main point, but Evocation has some out-of-combat utility that can benefit from the CL bump (cribbed from Treantmonk):

Floating Disk (Greater)
Force Ladder
Ghost Lantern
Glowing Orb
Contingency
Submerge Ship
Instant Refuge

Most of these benefit from increased CL-based duration. Some you really don't want to be dispelled, so CL bumps are good. All of them can be cast when you don't care about the rounds.

Thematic concerns: Charge beam is also used for utility in Metroid.

[The Dark Fiddler]

You could always research a version of the spell you want, but as an Evocation school. You need to work with your DM (which you should anyway), so if he's sticking close to the idea of what an Evocation spell should be you won't be able to get too much past him, but you should at least be able to re-school the orb spells.

[Zanos]

Do note that changing the Orb line to evocation instead of conjuration will prevent you from firing them into an antimagic field. IMO they're within the theme of the item enough that you should just ask your DM if you can use the item on them in particular without reschooling them.

EDIT:Also you may want to talk to your DM about this item in general. While having a higher caster level is excellent for buffs, crowd control, and utility spells, most blast spells don't really benefit from a higher caster level due to the damage dice capping out at fairly low levels. It could be more useful depending on the level of your campaign. It will help your pierce spell resistance, but if you're fighting something that is frequently resisting your spells, you probably have bigger issues at hand and can't really waste time charging up your spell. This is pretty dependent on what your campaign is like, but most combats for me don't last more than four or five rounds anyway.