Been looking at this power and it seems like some fairly glaring holes were left in its interpretation. Notably, that it seems almost useless with regards to any question that isn't strictly yes or no, with silence being damning. Any question with a "longer response", than that, could feasibly be checked or twisted by the speaker, or outright ignored.

In fact there doesn't even seem to be anything in the power that states that the target is compelled to answer the question at all (rather the opposite).

As a general example of why I can't see this power working particularly effectively.

Psyker: "Do you know anything about the parties involved in [insert heretical acts here]"

Target: "Why do you want to know?"/"Why should I tell you?"/"Maybe I do, maybe I don't."/[insert total nonsequitor here]/etc.

Or another example, when more specific information is needed:

Psyker: "How do I get in contact with your employer?"

Target: [fails Willpower test to lie]: "Well, first you need to get in contact with--" [immediately shuts up when he realizes he's starting to tell the truth]

I'm just wondering if I'm misreading the rules, or ways other GM's have of dealing with the gigantic gray areas this power seems to leave open. At BEST, this power's main point seems to be avoiding being misled by someone, rather than actually getting information out of them. Which, to me, doesn't seem to have been the purpose of the power.

Think of it as a lie detector.

The heretic/criminal/whatever can be pulled aside by the Cell and is being submitted to questioning, with their life at stake.

They'd better answer.

'Cause silence is damning indeed.

It is a rather interesting ability to be sure. I have never been a DM in a campaign where a player takes it, and only seen it played once. First off, you have to remember that this is only a minor power, with a threshold of 6, so its very easy to get off. It is also sustained, so you do not have to spam use it when talking to someone. In short, it is very cheap and easy to use. That is why I think that it is acceptable for it to have flaws. Yes, people can stay silent or mislead, but for such a cheep power, if they could not, it would be all kinds of broken.

The major problem with it is that it is called truth seeker, so you assume it will get you the truth. In truth ( ), it lowers the likely hood that you are being lied to. If you want to use it effectively, you will likely have to work harder then simply activating it. Try making the person angry, so while it is active they may blurt out something they would have lied about, or find a way (torture is always good) to lower their willpower. It looks as if it would work well in an interrogation setting.

I have only ever played one campaign with it, and it was actually way more harmful then helpful. It had major impacts 3 times before our psyker stopped using it. The first was early on, before our DM became warry of it. The psyker got a target of our investigation mad then used it, causing the target to accidentally spill the beans. Was useful, except the DM was not prepare for that to take place, and the campaign was abruptly ended way to early when we found the culprit one the first day. The second was in a later campaign, when we were looking through a hive city for a sister hood of witches. We asked a high ranking member of the church if he knew anything, with the power active. The priest though, was an overly proud man and got incredibly offended we would even suggest he would allow witches to live here under his watch. he refused to answer and kicked us out. With the power active, we assumed this mean he was hiding something, although he was actually 100% innocent. This lead to a string of unfortunate events which put our cell in the bad books of the church, eventually making us get chased off the planet by sisters of battle. The third time was ironically in the same campaign, vs the same priest. We confronted him again and openly accused him of knowing. This time, he did know, having done his own investigation and having found the witches. The problem this time was that he passed the willpower test to lie, and the power does not state the DM has to give any indication on if the test passed or not. The priest openly lied to our faces, saying he knew nothing, and we believed him. In the end we got chased of the planet, only barely managing to plant enough info for the church to find so they would accurately deal with the witches.
TL:DR: The power can really screw you over, and sometimes piss off the DM.

In short, the power is not going to simply give you the answer you seek, and is probably not intended to with the ease at which it can be cast. It also can be somewhat dangerous to trust. That said, it is from the radicals book, and I do noy believe it is actually meant to be super useful, as it is not a core power, and is instead just there to add some flavor, should you grow tired of the core rule book powers. I am not sure if I actually answered your question, but I hope that helps somehow.

Thanks Jeriko. The answer was informative, and largely confirmed what I had guessed about the power. Best suited to niche situations or interrogations where the target doesn't really have the option of staying silent or avoiding the questions.

Much like Touch of Madness, this power threw me off just because of the way the power is worded, vs what it actually does.

The way this power was played in my group was that I, as a psyker, could cast the power on an individual who would not know the power was cast. This would afford me roughly one sentence of truthful information before the target took the willpower test to lie. We played it as a way to extract just snippets of info from target without giving it too much power.