How to decide which "monsters" can be played?

[osteomancer]

@osteomancer its author fiat in the sense that as this is the world Butcher created, he gets to say how the world works.  Red Court vampires are literal monsters with human faces and white court vampires are humans with monstrous symbiotes.  You might as well say that the only reason Mab is the queen of winter and not summer is author fiat, because its on the same level of establishing basic facts about the world.

Yes, for his books he gets to do exactly what he wants.  I disagree with some of his choices, but I'm not making the decisions for the novels.  I am, however, deciding what happens around my gaming table, and I think the choice to allow White Court and not Red Court as PCs was illogical.  As a reader I may have to deal with author fiat, but as a GM I can make the (personally) more logical choice.

[toturi]

Doesn't a changling that takes all the requisite powers of his fae parent change into a fae and becomes an NPC, even if he has refresh left?

[KOFFEYKID]

Absolutely you can play a red court vampire, you can play any damned thing you want, you just have to come up with a feasible reason why you can play that. I made up this power to use for a red court vamp Im playing in PbP game. Mechanically, it removes Echoes of the Beast and offers a +1 rebate at the cost of possibly becoming and NPC is certain conditions are met, net gain is +2 refresh, turning an 11 refresh RCV into a -9 refresh player character.


Gifted With Soul [+1]
Description: You are different from other Red Court Vampires. Normally your kind do not have a soul, for it is antithesis to your being, and destroyed once you have had your first killing feed. You however have somehow managed to store your soul in an item, making a phylactery of sorts.
Musts: You must be a red court vampire, must have an aspect that reflects this power.
Effects:
Silence the Beast. You loose your Echoes of the Beast power. As a Red Court Vampire with a Soul your beast is suppressed by the morals other Red Court Vampires lack. You are reimbursed for the refresh cost of Echoes of the beast, since you no longer have it.
Refresh Bonus. You have somehow maintained your soul, keeping free will. Add +1 to your refresh level.
Phylactery. Your soul is stored in an item that you must keep on your person at all times. If it leaves your person, you loose the above benefits, becoming an NPC. You may spend one fate point to give you one days time to retrieve the item.
Altered Catch. You are no longer burnt to a cinder in sunlight, but you are weakened in it. In sunlight your catch is automatically satisfied for any attack. In addition add a new condition to your catch: "Phylactery Damage."
Made Whole [-1]. If you take this upgrade your soul no longer resides in your phylactery, which becomes a mundane item, it has been restored to your body. You loose the "Phylactery" portion of this ability, and the "Phylactery Damage" condition on your catch.

[Vertrucio]

Some of my players have expressed an interest in playing "monsters" and I would let them.

However, I'd basically use a situation similar to the TV show Angel, where that monster is cursed or somehow given back its soul and free will. But I'd also tack on an extra caveat, such as a Heavy Conscience or Filled with Remorse. Essentially, the worst thing you could do to a monster is to give it a conscience, a soul, and the full realization of all its horrific actions.

You could always throw in a big caveat, like "revert back into monster if you find true happiness" just to stick with my example.

You have to realize that a full blooded monster of any type really throws the power scale of the game, so you have to up some part of the game to match, or limit them somehow. It's up to you, the GM, to determine how to do that.