Feel No Pain and Perils of the Warp

[-Tom-]

The question here is more if FNP generated by a psychic power can be used to protect against wounds caused by a perils which is suffered during casting said power, not whether FNP can be used for perils full stop.

Yep, this.

It was a case that the Wraithseer would get FNP from the psychic ability he was using, upon himself. At the same moment though, he took the Perils. So the 'ordering' of what was happening may have been important as to whether he actually 'had' FNP at the moment of getting the Perils.