My party's Psyker picked up Dowse a while ago. This pretty much short-circuits any need to 'investigate' anything- the party can now just 'ping' the exact location of whatever they are looking for. Sometimes that can be a good thing- it keeps things moving and prevents the campaign from stalling out- but it can also be anti-climatic…

Currently my players are battling Pilgrims of Hayte who are attempting to topple a loyal Imperial world. They have spent the last several sessions preventing the Pilgrims' attempt to trigger a full-scale warp incursion, and are now preparing to hunt down the mastermind behind it all: the Pilgrims' False Prophet. I would very much rather that be more involved that just firing off a psychic power and making a b-line to his hidden lair. So, before I resort to the cheap trick of creating a brand new sorcerous ritual just to make the mission more challenging, are there any official, established means of thwarting divinations? All that I've been able to find is one psychic power that foils vision, but not psychic senses. For the record, the False Prophet employs a Sorcerer that specializes in 'bindings'- trapping warp effects or entities in objects- so I've laid the foundation for, say, making a certain psychic power permenanty functioning within a limited area.

Suggestions?

I don't know of any official means of thwarting divination, but you could make the False Prophet and his Sorcerer exist in a small pocket dimension of the warp bound to their fortress or base of operations. If the Psyker tries using Dowse, you could have him gain Insanity.

Its not an official solution, but I hope that helps nonetheless.

Dowsing is a powerful discipline, and easy to use, but here are a few things that might throw a kink in things:

1: Create a new unhallowed relic (see p. 119 DotDGs) that the leader wears and would make him invisible to Dowsing (don't worry about the PCs getting their hands on it…the moment they do, if ever, the person must make a very hard (-30) Willpower test or gain 2d10 IP & 2d5 CP just for handling it…if they decide to keep it and they made the WP test, just give them the IP&CP as eventually it will get them).

2: Create a new Sorcerous ritual which will probably have a threshold of about 15 and last for 2d10 hours (note that this involves the sacrifice of a believer of the god-emperor, so no it's likely a ritual the PCs won't use, unless they like IP&CP as shown in example 1… and would be the ritual used to create the artifact shown in example 1).

3: Make the leader too powerful… so if you just want to go straight to him, then all his lackeys are there, whereas if they hit them a bit at a time, they could take him piecemeal…but the players may not be bright enough to figure that out…a well timed Logic roll here, might lead them to this conclusion. If not, the leader, who is probably a Master Sorceror, with 2 or 3 apprentices, sorcerors in their own right, and at least a dozen guards, with appropriate leaders amongst them… yeah that's gonna leave a mark. And cause a few burned fate points.

4: Give the leader a Null who works with him and stay handy until they actually do their thing (hey, it worked for Eisenhorn). If the leader is constantly around the Null, they'll never be able to Dowse the guy…but don't give it away, let the party figure that one out (no Logic roll here).

If that doesn't do it, hopefully those will spawn an idea or two that will.

Denmar's ideas are excellent, and I think I'll be stealing some of them in the near future ;-).

However, I think most of the time you can just beat Dowsing "by the book": it only works if the subject is within a number of kilometres equal to or less than the Psykers Perception Bonus. Now even if he has specifically maxed perception (Psyniscience is Per as well, after all), this will leave you with a "scanning radius" of 5 or 6 kilometres at best. Considering the enormous size of e.g. a Hive City, your Acolytes probably won't be able to find someone unless they already have a pretty good idea of where to look for him anyway. And if they do, the secret underground lair of your villain could just as well be 5 kilometres underground, which to me doesn't seem at all unrealistic given the scale of the setting. And even if the psyker is able to figure out that the lair is "5 kilometres below", that still leaves them with the small matter of actually getting there.

Of course, if your psyker is sufficiently crazy and / or stubborn (like the one in my gsmr is) they might start doing a grid search. But if you actually insist on having them play that out they'll pretty soon start to figure out that it isn't a very efficient plan (even a comparatively small city of 150x150km would be 900 stops with a PB of 5, my group got bored after the third stop).