custom vampire-esque race mod help

[codissius]

So I am attempting to make a large story/location mod, but I would like one aspect of the mod to be the choice of adopting new powers. By this, I mean something similar to werewolf/vampirism, where you are usually normal (with possible buffs/debuffs), but you can transform into a new "race" with new powers and such. Where would this fall under in the CK and where could I find help/tutorials for this? If not, my mod will be pretty cool still, but much much less so as it would require a change to my storyline.