Nullification

[SpanielBear]

How about seperating the penalties? There are two main risks associated with psychic tests, the test against the will power, and the fact that a psychic action is itself a risky action.

Assuming that one avoids failing the risky action (i.e. gets more sixes than ones), then the psyker is assumed to have avoided the perils of the warp. Messing up their powers leads to (recoverable) willpower damage.

However, failing the risky action should have different consequences. This isn't about the strength of the psykers mind, this is about the dangers of the warp. Why not use a risky action table here, same as for grenades and plasma weapons?

[MarcoSkoll]

Personally, I would sooner go for a complete rewrite of the psychic rules. As it is, a psyker's control and power level are both represented on the Wp stat - and while one could expect that a more skilled psyker can manifest more power safely, the "safely" isn't in that sentence at present.

Now - expect some wittering -but I'd borrow the Power Threshold from DH, also would probably also keep something like Difficulty level from Inquisitor. So, testing whether a psyker has channelled enough power and whether they've manipulated it correctly become separate tests.

The reason is, there will be some powers that barely require any psychic energy at all but which are also very tricky, or some that need huge power but very little control. Picking a lock with Telekinesis, for example - Very little power, but very fine manipulation.

So, in this case, nullifying a power tests against the power roll (much like a dispel in WHFB), rather than against the control roll. Although I might also include a Wp test on the part of the dispeller in order to actually focus their talents in an attempt to dispel

I'd say the maximum dispel power a psyker can muster is decided by their own psy rating. After all, no matter how controlled they may be, an Iota level is going to have their work cut out keeping an Epsilon level at bay.
And at that same point, the power of a psy-negative can also be defined in dice (although they would have to automatically nullify, with no Wp test) - this would allow more variables than "Pariah or not".

I guess you can also include "area dispels" by losing dice from your psy rating (whether positive or negative), the further away it is. For example, if you're Psy rating 4, while you could nullify a power directed at you with up to 4 dice, you'd lose a die for each X yards away something else you wanted to nullify was.

As far as failures, I'd scrap the Risky actions. I'd then have some kind of "miscast" like thing for the Power roll (depending on what numbers come up. Perhaps a certain number, or perhaps doubles/triples/etc), and some other consequences for failing the control test.
I'd also suggest modifying the roll on any "failure table" by the degree of the failure, just so a psyker who fails by a mere 2 points doesn't end up summoning a legion of bloodthirsters by mistake.

I might pen something more solid when I find the time, but I quite like that as a start.

[GAZKUL]

alternatively you could avoid the problem by taking a Pariah as your main character.....

[Aurelius 12]

I'm not sure I see what the big problem is with regular psykers nulifying things as they do now- afterall it's not like they automatically stop an opponent, simply make it more difficult. I really like the idea of a psyker halving their Wp for every attempt though.

It strikes me the most elegant solution would be what Dolnikan seemed to suggest in a roundabout way; why not just make Nulify a ranged ability.

That, combined with the halving element, seems to make Nullification potentially very effective, and potentially very dangerous. Especially if you made it risky (i.e. the player rolls a D6 before they even try nullification) combined with SpanielBear's table (or an adaptation thereof) for the nasty things that happen to you if you screw up.