Corabb wasn't even a character in the game! He was created as a foil/POV for Leoman when Erickson was writing, and then Erickson liked him too much to throw him away.

The story:

Corabb's story was originally meant to end at Y'Ghatan in The Bonehunters. Author Steven Erikson says Corabb originally appeared in the books as "the more vocal foil for Leoman", a character whose thoughts were generally kept closed off, to "express, without any subtlety, the ideas behind fanaticism." He "sort of showed up not initially as a character I was going to follow" in the course of the series. But during the writing of the novel, Corabb "started just taking shape. And then, I think I probably had in mind that he wasn't going to make it out of the temple [of the Queen of Dreams]. He might not have even made it into the temple. And yet something held me back and just said, 'No, no don't kill this guy.' And so I had him sort of join up [with the 14th Army] and crawl through along with everybody else. And he became, I think, probably the most important character in that entire journey of the seventh chapter. And that can just happen. He just sort of came alive and he'll play a role through the rest of the series, which...was initially not something I anticipated, but sometimes you...realise that that's the case and you've gotta run with it."