Completely disappeared without a trace. And deserters, who should have been brought back from previous installments of Heroes.

It wouldn't hurt to bring back the evil sorceress, poisonous creatures, mermaids, and sea monsters. If all of the above were to be reintroduced, it would require creating another dozen races. And there would be about fifty neutral creatures. Although, that would be pretty cool. You play, and there are always new and new faces...