|
I haven't been there for awhile, so I'm not sure how active a poster he is these days, but Monte Cook, writer of the BoVD and likely inventor of Rallaster, used to answer questions at his own messageboards pretty frequently.
Barring any conclusive data on the god, I'd look at very similar gods, such as Loviatar from the Forgotten Realms, Zon-Kuthon of the Golarion setting or even just watch a few Hellraiser movies and think 'what would a cenobite *god* be like?' You might be able to get some inspiration from looking up Xipe Totec, or other Mesoamerican figures, whose priests often commited acts of bloodletting or self-mutilation to bring themselves into what they saw as a holy state of consciousness.
A priest of Rallaster (Loviatar, Zon-Kuthon, etc.) would likely follow very much this line of thought, that pain is sacrifice, and enduring pain is a sign of strength and devotion, and that the focus they derive from inflicting pain upon themselves helps them concentrate to regain their spells (and they'd be so skilled at such activities that they would be quite likely to be able to inflict pain upon themselves without causing hit point damage, or, their 'prayer time' could be at night, just before they sleep, so that they can recover some of the nonlethal or lethal damage they do to themselves overnight, in extreme cases).
Only in excruciating torment, when the body and mind recoil and waver at the edge of conciousness, does the priest of the Paingiver see the face and hear the words of their god.
As a result, they would also consider inflicting pain upon another as being a sacred act, and no act of sacrifice would be painless. Indeed, a painless swift death might even be considered a sign of utter contempt, denying that individual a moment of communion with their god!