Mixing PfP

So, If I understand the new PfP correctly, units belonging to a detachment from the Dark Eldar codex use the Dark Eldar PfP, while units belonging to a detachment from the Covens Supplement use the Covens PfP.

Master of Pain effects the Haemies Unit, so friendly models in his unit I'd suspect.

So if you have a Haemy from the Covens list, join a unit of say Incubi from the Dark Eldar list on T1 (T2 with Master of Pain) then since the Haemy becomes Fearless, I'm assuming that the Incubi would now be Fearless including having FNP 6+?

This could be a good way to mix fearless throughout out fragile units.

-Fioater

It would work as long as the special rule in question was one of the ones that spread to joined units, sure. Not a bad way to get Fearless, if that's your goal.