Helm of Spite vs. Grey Knights/Daemons

Somewhat surprised this hasn't been discussed yet:

Grey Knights can cast Sanctic powers, only suffering Perils on double 6s when everyone else would suffer Perils on any doubles. Similarly, Daemons can cast Malefic powers, only suffering Perils on double 6s when everyone else would suffer Perils on any doubles.
Our Helm of Spite causes psykers within 12" to suffer Perils on any double. How do these interact? Does the GK/Daemon ability take precedence, or does the Helm? Something for the FAQ?

Specific vs general. The brb is trumped by the codex, in this case.

The GK and Daemon exception to the rules in Daemonology are specific to that, and would need to give extra exceptions to apply to the Helm.

Right, but Grey Knights have the army-wide special rule Purity of Spirit, essentially stating what's written in the BRB (I presume Daemons have a counterpart), which makes it codex vs. codex.

Purity of Spirit:

Quote :

In addition, unless otherwise stated, when attempting to manifest psychic powers from the Daemonology discipline, Grey Knights Psykers only suffer Perils of the Warp if two or more 6s are rolled when taking a psychic test.

Helm of Spite does state otherwise.

Right, I guess that settles it. Thanks.

And Daemons don't have an equivalent to Purity of Spirit, to my knowledge.