The Temple of Storytelling: Character Creation
Christopher La Porte

Agree with the unboundedness thing.

One of the reasons the Quran is such a shoddy, over-rated piece of fan fiction, is because some of the best characters from the Hebrew Bible and Christian New Testament are ripped out of context and turned into dull, lifeless cardboard cut-outs.

One of the most egregious examples is Job, who changes from a complex heroic archetype into a spineless, quivering, sentimental sack of saccharine schmuckbuggery.

By all means borrow old characters, but make sure you actually transform them and give them new life, rather than murdering them!