if Extra Arm becomes a mental advantage would that prevent Possessor from using it?

[Plane]

Possession normally gives complete control of all physical advantages, so there doesn't seem to be a built-in way to cover the idea of "if I inhabit the body of a creature with an extra pair of arms I won't be familiar with their use"

I know that mental advantages aren't transferred though, so if we used "Physical and Mental Abilities" (Powers 154) and applied "requires IQ roll" to Extra Arm, would it make sense that only the original owner is able to move that arm?

I don't know if it would make sense for this to allow you to bring extra arms into other bodies though, like maybe it's "both mental and physical" so it only works in the original body with the original mind?

I figure if applying something like Unreliable or Requires (Attribute) Roll to Extra Arm it could operate more like "failure makes the arm immobile" rather than "failure makes the arm vanish" unless you also took something like like Switchable +10%

Being unable to use limbs seems to be (B141) of equal value whether it's lacking that limb (ie Lame: Legless) or having that limb be an immobile target (ie Lame: Paraplegic)

The benefit of "conceivable that you could regain the use" is meant to offset "can be struck for damage" so it seems like "present but immobile" should be the default state for temporarily unusable limbs (ie as if it were crippled) but that the Switchable +10% gets you the "best of both worlds" (can be untargetable yet regainable) but then it's going to cost a Ready to vanish/restore your non-usable limb unless you take Reduced Time enhancement.

If you were able to actually switch on an extra arm not just in your home body but also in others that's probably some kind of Cosmic enhancement? I'm just thinking of a way to make your bonus arms harder to use for those not familiar with that kind of complex nervous system.

Basically if the IQ roll is hard you might have a skill/technique for using the arms that you can built up to make it unlikely you'll be failing or needing to spend a lot of FP to maintain it.

[naloth]

If you had to buy off a -4 or so familiarity penalty as a perk (each body being a different perk), I'd call it a -10% limitation. Basically you're getting 10 points off which should make up for buying a few perks for the bodies you use often.

If it only applied to extra appendages you haven't used before until you've spent a day or so getting used to them, it's just a quirk.

If you want to manifest physical traits in your new body, I'd use an affliction that only affects your host body which can be made "always on" for as long as you inhabit the body.

[Pursuivant]

Originally Posted by naloth

If you had to buy off a -4 or so familiarity penalty as a perk (each body being a different perk), I'd call it a -10% limitation. Basically you're getting 10 points off which should make up for buying a few perks for the bodies you use often.

RAW Mind Control and Possession says nothing about problems with possessing bodies with different morphology than your own. Presumably, you just tell the host body's brain what you want it to do and the host performs the task as it would normally.

If you do have problems dealing with hosts with different morphologies, Naloth's suggestion is a great way to handle it. Possibly base Perks, Quirks, or Limitations for different morphologies on categories listed for Non-Humanoid Hit Location Tables (p. B552). Alternately, base them on particular campaign species if you've got non-humans with very different physical traits.