The Icewind Dale games probably had something to do with Interplay losing the d&d license in the first place. Just too many invented, non-d&d creatures, spells and rules exceptions. Non meaning you could'nt find many of the things they created in any of the rule books. Nothing wrong with being creative, of course, but when dealing with such a rich, widely known intectual property they should have tried to stay on track. By doing weird stuff like taking away undead level drain in IWD1 and implementing really just half assed 3d rules in IWD2 they did'nt do themselves any favors... Wotc did'nt like this one bit. Bioware has always used d&d rules in a respectfull, traditional fashion(always getting everything approved by Wotc) and could probably retain the license for some time to come. And yes yes... many of the Obsdian guys are ex Interplay/Blackisle guys but in the current context Bioware is the parent company and one would think mistakes of the past would not be made. Plus the main rules meister of old is gone...
