Dreaming and GURPS

[Tinman]

1) The plausability of brain attack would depend on the exact type of attack.

Frex: If the innate attack is a spike that will shoot out your wrist "wolverine" style. You will need to make sure that your arm goes in it's mouth fist-first & not broadside. As GM I'd requre some kind of roll to hit it's mouth to ensure orientation.

If on the other-hand, it's an attack of the nature of your arm exploding.
There's no rolls needed. However by raw that would be an internal explosion:
no DR & 3x damage.

2) GURPS campaign related: yes.
GURPS rules related: no.