So I've noticed that with fettering and reroll talents, that phenomena and perils *never* occur in my group, to the point of we've had the psyker reroll 4 times including one fate point and had nothing happen. Since the psyker is one of the most combat capable in the killteam (holocaust against daemons, blood lance ignoring TB and AP, and opening warp rifts everywhere) the one "drawback" just isn't a "drawback" when you can reroll it 4 times.

I don't want to outright say that those talents can't be used because librarians *do* have better control. My question is how do I make it so that phenomena are more likely? With a xenos focus on this campaign, thinning the veil isn't the most likely answer, but maybe certain xenos can disrupt psychic focus or something like that? Perhaps eldar forcibly disrupting his warp sense causing him to push instead of fetter? Unknown xenos species that can slightly exert mind control that means he can't reroll and he can't fetter?

I'm pretty sure there are nominally Chaos-aligned powers/effects that cause phenomena to trigger much more often/automatically, or increase the likelihood a phenomena will turn into perils. Xenos psykers could learn an equivalent technique to deter enemy psykers.

I would not, however, do something like causing a push instead of fettering or removing the ability to reroll or fetter without any chance to resist or to know about it.

Psychic disruption devices - automatically downgrade all powers used in their area of effect by some amount of PR. If all powers are automatically used 3 or 4 PR, well, it suddenly gets a whole lot harder to do stuff.

As far as wanting to up the risks ... double check that all the reroll abilities they're using stack. Also, one could introduce a houserule that if you trigger phenomena, reroll to avoid phenomena but the reroll also triggers phenomena, you roll on the phenomena table with a penalty; if you reroll again and escape phenomena, you loose the penalty but still roll, if you trigger, the penalty increases, reroll again and escape all the penalties go away, but if you trigger again penalty goes up.

One could also introduce/make sure to enforce that whatever amount of Power Rating you apply towards using a power is the Power Rating used for calculating all effects from that use of the power - IE, you have PR 6, but cast at Fettered PR 3, you're treated as having PR 3 for all purposes for that use of that power.

This, while not directly upping the risk, means that Fettering remains useful, but it also means you're casting at less than full strength - this means that for the little stuff, they can stay safe, but when they want to do something bigger, they have to run some risks.

That said, phenomena and perils can be incredibly disruptive when they do occur, so I fully understand why players will go to significant lengths to avoid triggering them.

I like the idea of not being able to use higher PR powers with fetter, also how exactly do those powers work? Or rather, what book would I find them in? Maybe names as well.

Also, do you think fringe Inquisition factions would have weapons that turn a psykers power against him? I.E every time he attempts to cast within 1d10*PR meters of a weapon with the Warp Disruption quality the powers have a chance to reflect back onto him instead of the enemy?

I also remembered if the psyker crosses paths with certain inquisitors he could end up at the business end of a witch stake wielding death cult assassin, though that's if he clearly shows he's a filthy mutie

AoE Psychic disruption devices ... are, I think in DH's Radical's Handbook. The ones I'm thinking of are larger, fixed emplacements, though. On the other hand, they reduced the effective PR of powers by between 1 and 6 levels in a fairly large area (in DH terms, they reduced the number of dice rolled by 1-6 d10s), depending on how much the owner was willing to budget for it.

DH's Inquisitor's Handbook also has the Witch-lance (the Inquisitorial Miscellany section), Ascension has that anti-psyker crossbow; Daemonhunter might have a few things too. I think Blood of Martyrs might have some anti-psyker stuff too.

The Culexus Assassin is, I think, in RT's Navis Primer. If not there, probably in either BC Core or BC Tome of Fate. Khorne hates psykers, so there might be some stuff to borrow in Tome of Blood.

I think some of the Eldar NPCs, especially the Farseers and Warlocks, have items that negatively impact enemy psyker power uses near them.

Untouchables are statted out in various locations. There could also be an inferior form of Untouchable-like mutation/ability, that somehow suppresses, or otherwise makes harder, the drawing of power from the Warp.

...the one "drawback" just isn't a "drawback" when you can reroll it 4 times.

Not to focus on one specific point but how the hell does someone get FOUR rerolls in anything? AFAIK, universal rule with most gaming systems is that you cannot reroll a reroll. Additionally, fate points RAW can only be used to reroll a failed test once. A roll on the phenomenon table is not a test and is a random result therefore cannot be used to change that. The player can however, use it to avoid getting the WP test result that required them to take the phenomenon roll. Other psychic based talents which might come into play:

• Strong Minded - Only allows a reroll to resist mental attacks. Again, links back to the test
• Rite of Sanctioning - As long as the phenomenon roll doesn't go to perils, you can sub in your chosen phenomenon.
• Favoured by the Warp - Roll twice and pick the more favourable result. In theory can be used with the above.
• Warp Affinity - Can't be taken if sanctioned and would let them drop a phenomenon result they didn't like in exchange for instant corruption.
• Warp Conduit - When pushing, more power and less chance of hitting that perils region.

So unless I'm misreading this and thats over the course of a single encounter using various tricks per round, there might be one of your issues. Players should not have four chances to deny things going wrong.

That aside, if librarians do spend all their time using powers at the low fat setting, that's plausible and nothing that can be done. The thing that needs to be made clear though is that when they do use powers like this, they can never tap into the deepest realms of power that they could achieve and you can use that to your advantage if there is a particularly potent enemy sorcerer who does not have the same concerns for fettering and they will need to tap into those reserves to stand a chance of beating their mental defences. Case in point, greater daemons or, if you wanted a psychic-like xenos nasty, an avatar of Khaine. Lets see fettered powers try to hold their own against one of the nastiest non chaos big things out there. You can either make your own stats for it or there's some existing ones which can be adapted somewhat in Rogue Trader - The Koronus Bestiary. Hint, hundred plus wounds, lots of fiery pain and death.

Consider meanwhile the reworked Perils table which came into effect from Black Crusade onwards. One of the new fun results is the 91-99 result of "Grand Possession/Incursion" which tl;dr means a greater warp entity tries to take over. If succeeds, bad stuff. Even if failed, some permanent stat damage and due to the savage effort by the daemon they permanently roll higher on the phenomenon and perils table.

If however you want to screw them over and force some phenomenon, as above, psyk-out grenades would be a good start. Stats for them are in DH - Daemon Hunter. Effectively the short version of what they do is that anyone in their blast radius makes a willpower test with some nasty penalties and for each DoF, lose points from their PR for a good few hours and if they lose enough, the next time they try to manifest powers, auto trigger phenomemon. In Rogue Trader though they have been changed and when used by a Culexus Assassin, do high damage to anything with a Psy Rating thats hard to resist and inflict Willpower damage. Purgatus Crossbows from Witchhunters do similar, lots of damage to anything with daemon trait or a psy rating, however IIRC (can't find my **** 3rd ed codex), they did inflict a phenomenon save. The Imperium have these and as do Dark Eldar, in fact Dark Eldar have a lot of anti-psyker weapons given that they shun psychic techniques of their Eldar kin and is highly likely that some combo of drugs and cocktails will mess with psykers when used.

Existing Imperial Drugs meanwhile, look into Spook. Effectively causes some insanity and gives non psykers a brief minor psychic ability. For full blown psykers though can cause more insanity and add a major +X impact on the rolls. Nowhere does it state that a marine is immune to the effects of narcotics, they just have many resistances to.

I have however, saved the best till last. If you are determined to cause some major psychic pain to the librarian which, if unchecked will turn fatal, consider Enslavers (Deathwatch - Ark of Lost Souls). These are some of the nastiest psychic beasts in the known galaxy bar none. A psychic being that can transcend realities, they tend to get together in small conclaves and can target a psyker to use them for their own ends. They will generally focus on weak minded psykers or those of interest and start to form a psychic link with the victim. In some cases the victim isn't even aware that this bond has been formed. Over time though that bond will grow stronger and the Enslavers will either use the victim as a tool for their own ends or (most likely) a physical bridge to allow the creature to manifest in our world and continue that pattern. They are parasitic in nature, taking over a victim and using them as a host to serve as a method of bringing more of their foul kind into reality. Additionally, it does state that Sanctioning is not foolproof against enslavers. It is a potent barrier but enough of these things working together will easily overwhelm the sanctioning efforts put into place. Powerful tools able to exert substantial control on lesser beings.