I think that every so often, at least for monsters that don\'t appear another way, portals akin to those the different races supposedly came out of would appear, possibly with a \"disposable\" npc coming out (disposable meaning it doesn\'t talk, drops no weapon if you kill it, etc.) being chased by a herd of monsters... That would be considered by some to be \"popping out of thin air\" but it would have some connction with the setting, showing how monsters came into the world with the races, possibly offering some connections between a race and a particular monster, such as a monster that came from the same world as a certain race that has a poison attack. The poison attack would work on almost every race except for the one who came from the same world as the monster, who has built up an immunity.
Just my $0.02... wait... $2.00. Durn inflation.
josePhoenix