in oryx.cs find:
Code:
WmapTerrain.Mountains, Tuple.Create(
100, new []
{
Tuple.Create("White Demon", 0.1),
Tuple.Create("Sprite God", 0.09),
Tuple.Create("Medusa", 0.1),
Tuple.Create("Ent God", 0.1),
Tuple.Create("Beholder", 0.1),
Tuple.Create("Flying Brain", 0.1),
Tuple.Create("Slime God", 0.09),
Tuple.Create("Ghost God", 0.09),
Tuple.Create("Rock Bot", 0.05),
Tuple.Create("Djinn", 0.09),
Tuple.Create("Leviathan", 0.09),
Tuple.Create("Arena Headless Horseman", 0.01)
and add your mobs in there. You can probably check the gods XMLS to see if you need to add a new tag there aswell.