Roleplaying and the killer gnome

[Malroth]

New campaign is starting and I'm considering a gnome shadowcraft mage. And while I'm familliar with the mechanics I'm wondering how to play this character in the times that he's not in the bowels of some tomb. He's a middle aged 3 foot tall genius scholar, yet he's diving into mortal danger along with people 1/4 his age to find treasure. He's a member of a class whose power stems from an innate understanding of reality yet he deals in illusions and falsehoods. I guess what i'm asking is, what makes this character tick how can I run a killer gnome and make him more than earth-spell-metamagic-school-focus-heighten silent image becomes the exact perfect summon spell for the moment.

[Tvtyrant]

You could run him as an extremely dreamy, far away sort of person whose particular talent with magic has made him worse at distinguishing well between his own mind and reality. Say he had a naturally unfocused personality, with his head up in the clouds, and then developed a talent with shadow magic that makes his cloudy view of the world enforceable. If he imagines something, for him it is only natural for it to come into existence and then disappear as soon as he no longer thinks about it (fluffing spell durations, for instance).

Or the opposite, he is extremely idealistic and wants to force the world to match his ideals. His magic allows him to do that, and he frequently makes use of his magic to force the world to match his expectations.

[Darrin]

He's a member of a class whose power stems from an innate understanding of reality yet he deals in illusions and falsehoods.

I'd go Full-On Nutjob. Some years ago, he got a little more than a peek into the Far Realms and how fragile the "real world" around us really is, and it cracked his brain in half. Prime material, shadow-stuff, it really doesn't matter, all this crude stuff around us is just some Elder God dreaming, or really having some kind of nightmare, and when It wakes up, then everything is really going to hit the fan. As for why he's adventuring: "Got a telephone call from Azathoth, man. I gotta get into this dungeon and lick the walls, or the little purple trollpixies that live in my third elbow are going to destroy this sub-continent with a deluge of bacon-flavored watermellons."