Open Terrain Generator (otg) random spawns

Hi there!

i am going to use the plugin Open Terrain Generator for my server,
and i heard somewhere (but i forgot where) that i was able to make mythicmobs spawn in CUSTOM biomes,

for example,
i make a unicorn,
and you can only find it in the enchanted forest biome

is there somebody that could write a random spawn example?
i can't get it running...

Thanks
AnimalMace