the fighter thief is my favorite combo. I first used a dual class and then multi id have to say i liked the multi better. The thief abilities you gain at higher levels make your character awesome. The fighter part allows your overall attacking to be better which added to a backstab multiplier ... you can predict the outcomes.
I never used to be a big trap user but reading the diferent threads, traps are an awesome ally so havin a multi F/T allows a good use of traps.
if your after justa straight answer,
multi class
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Nor shadow or myst
the jester is a myth
he is absolute
beware the jester