I was looking through the rogue trader book and in it there is the untouchable package which lowers the psi rating of psykers around you for each rank you possess in it. What happens to a psyker if an untouchables rating exceeds his psi rating?
TLDR the psyker is screwed.
First of all, does Rogue Trader actually have an untouchable package? I only see it in the Radical's Handbook and that's a Dark Heresy source.
Rogue Trader mentions it in a table on page 172:
Untouchables: An Untouchable reduces the Psy Rating of any psyker (within 5 metres) by 5. All other rules for Untouchables are unchanged.
The Rogue Trader rulebook doesn't mention any specific issues with negative psy rating, and neither does the errata.
But keep in mind a few things:
- You add psy rating x5 to your focus power test, and with a negative effective psy rating that's a penalty. You are much more likely to fail.
- Most of the powers will have no effect with psy rating of zero or lower because it acts as a multiplier on a base figure for range or damage.
Personally, I'd rule that one needs at least 1 in effective psy rating to actually manifest a power, and that trying to manifest a power while at zero or less effective psy rating leads to a psychic phenomena.
Note that effective psy rating can be boosted by a push back to positive numbers, so there is still hope for a psyker near the untouchable.