What sort of issues would I run into if I wanted to co-opt some D&D 3.5 creatures into a D20 Modern setting? I'm looking mostly at devils, demons and some of the astral creatures.
Will such creatures likely need re-balancing, or should I be able to get away with throwing them in with few if any changes?
Alternatively, is there any existing material that describes these sorts of creatures that is made specifically for d20 Modern?