Shut up and give me all your monies and fineries.
Thief is all in the name. Well mostly. It is true that Thief is what he is, and an amazing one at that. Whether it's stripping the gold walls of a castle as they walk by, or stealing things that don't actually exist, Thief can and has lived up to his title.
Yet, he's also the only character that, at least initially, was actually on a heroic quest. That quest disappears rather early in the comic, not because it was forgotten, but really because he completed it! Yes, that's right, a Light Warrior, in a comic where comic failure is rampant, common and expected, actually successfully completed a quest without it back firing horribly or unleashing a far worse evil on the world. . .
Wait, it meant Thief wasn't bound any more. Forget I said anything about that last part.
My point is when we're introduced to Thief, he is on a noble quest. Doing it in the most Thief way possible, of course, but it is noble. His father, King of Elfland, is ill, so he's out collecting funds to finance a cure. Which only makes sense because Elf logic (serious, isn't pulling all the stops for a cure kind of the thing you do for a king anyway?). He does this by stealing everything that isn't nailed down. Then going back for the stuff that is.
Of course, eventually the quest is over, though not until after the worst pun ever kills the villain behind the King's illness. At that point, Thief is freed from his obligation and he becomes the avatar of Robbery we all know and fear.
That said, of the all the characters, he is the most practical. Yes, he leans heavily on the "can't have it, steal it" line of thinking, but you can't argue with how successful he often is in that regard. He also acts as a moderator for the more, um, impulsive and insane ideas of the rest of the cast, giving them more focus when the time comes. Then he takes off to hide because he knows he's just cannon fodder otherwise.
He is the team's leader, despite the fact that he got that role by stealing it. He is very effective at it and the group dynamic kind of needs him or they might just not make it all.
Which isn't to say he's a good guy, oh dog no. Evil might be a stretch, but he is classicist, racist and arrogant, to a hilarious degree. And he can be influenced to feed into his lesser desires. His hatred of dwarfs combined with Black Mage's desire for death and destruction resulted in a campaign of genocide across the Dwarf Kingdom. Given the lack of any kind of law enforcement in a small town, he took on the role, of a mob boss. Placed on the kind direction of White Mage, he's actually develops an excellent economic restoration program that doesn't involve stealing anything from anybody. Truly he was cursed.
Ultimately, he gets what he deserves. The only Light Warrior to not really earn his class change, he is made to pay for it at the worst possible moment, but having it stolen from him, by himself, from the past. Only fitting I suppose.
Thief does get overshadowed by the other cast members though. He is often the straight man to their madness, and as straight man, gets more forgotten than not, but when he shines, he shines, and that will likely cost you a small fee to witness (it was in the contract he forged your signature to).
Next time, the character who can't walk down a hallway without getting lost. Until then kiddies.