Daemons have no psychic defences whatsoever therefore the chances of Grey Knights getting to actually use their powers are pretty damn high.
This high in fact,
Leadership 10 - 91.67%
Leadership 9 - 83.33%
Leadership 8 - 72.22%
If the abilities don't go off just consider it an early Christmas present, however always presume that their going to ;-)
Now onto the Grey Knight psychic abilities that the Daemons need to be aware of,
Grey Knight Grand Masters and Brother Captains.
Hammerhand - Your going to be getting hit at S5 (or S10 if they have some kind of Hammer) 91.67% of the time, sorry but that's just the way it is. That means your going to be getting wounded on 3's or 2's for the most part and even your Nurgle units are being wounded on 4's.
Each WS 6 Grey Knight attack Vs single wound Daemon. (we'll presume a 5+ inv. save for the Daemon as this is most common).
Vs. T3, 0.89 chance of hit, 0.74 chance of wound, 0.49 dead Daemons.
Vs. T4, 0.89 chance of hit, 0.59 chance of wound, 0.39 dead Daemons
Vs. T5, 0.89 chance of hit, 0.45 chance of wound, 0.30 dead Daemons
It obviously wont be as bad if the Hammerhand user is a lower Weapon Skill but it still is going to increase the Daemon casualties.
Editors Note : This (though bad) isn't as bad as I was expecting...maybe there's hope for the Daemons yet...Thank goodness for that crappy invulnerable save, lol.
Psychic Communion - The Grey Knights can effectively modify their reserve rolls by one in either direction. This is obviously going to give them considerable control over when things arrive meaning they can be extremely proactive when reacting to other reserve based armies like Daemons, Jump Pack Blood Angels and other 'drop' lists
Lord Kaldor Draigo also gets Sanctified Flame which is a template psychic shooting attack that wounds Daemons on 2's. Daemon players should already be scared of Flamer templates so this isn't a massively big deal to be honest.
Brother-Captain Stern gets Zone of Banishment which he can use instead of his close combat attacks. This has a range of D6" and effects all models (friend and foe) but not himself. Anybody effected takes a strength test or is removed. This is bad for most units but is especially annoying to Daemons as they have to re-roll any that they pass.
How bad is this going to be for Daemons?
Strength 3, 75% chance of removal
Strength 4, 55% chance of removal
Strength 5, 31% chance of removal
6's always count as failures in characteristic tests so any strength higher than 5 has the same 31% chance of removal. So you have a nearly 1 in 3 chance of losing your 250 point Bloodthirster and there's bugger all you can do about it...
Hammerhand - See Grand Master/Captain entry above...
Heroic Sacrifice - When the champion is removed as a casualty he can take a psychic test to use this ability. He then gets another attack against one enemy model in base contact that if hits removes the target as a casualty with no saves of any kind allowed.
This could be an annoyance...How annoying?
Psychic test at Leadership 10 is a 91.67% chance of passing,
Weapon Skill 7 is hitting pretty much everything that isn't a Greater Daemon or Daemon Prince on 3's giving a 61.11% chance of taking a model with him.
Against Models of equal or higher weapon skill to him this drops to 45.84%
So on pretty much the toss of a coin whatever kills him dies as well or even something that didn't kill him but happens to be in base contact.
They get Hammerhand as standard and can pick any of the other psychic powers from their list at 5 points each. All of these abilities have their uses but the one Daemon players need to worry about is this one,
Dark Excommunication - Used in the assault phase before any blows are struck this ability robs the Daemon of any Daemonic gifts it possessed. Unfortunately most of a Daemons useful combat abilities fall under this classification. Bloodcrushers and Bloodletters lose their Hellblades and therefore the Power Weapon effect attached to it. Daemonettes and Fiends lose Rending, Plaguebearers lose Poisoned weapons and so on.
On the bright side however it's likely that most Grey Knights players won't be expecting to play Daemons every bloody game so will probably have taken more generally useful powers. It's worth looking out for on your opponents army list though ;-)
Hammerhand and the Dark Excommunication ability mentioned above as well as Sanctuary...
Sanctuary - Used at the start of an enemy assault phase this turns the area 12" around the caster into both difficult and dangerous terrain for any unit attempting to assault units 'friendly' to the caster. This has the added disadvantage of reducing any of those units that don't have 'assault' grenades to initiative one. Which is unfortunately most Daemons...
Though not a psychic ability this is as good a time as any to mention Corteaz's 'I've been expecting you' rule. If an enemy unit arrives from reserve within 12" of Corteaz and is within his line of sight him and his unit get a free 'out of sequence' shot at it. Making scattering into that 'bubble' with your Daemons a dangerous prospect should Corteaz have any decent fire-power in his bodyguard.
Cleansing Flame - Used at the start of the Assault phase before any blows have been struck. Causes a wound on a 4+ to any enemy model involved in the same assault (you still get your armour save save though) and any casualties count towards combat resolution. This will mathematically speaking kill a 1/3 of any 5+ inv save Daemons involved in that assault before they get a chance to do anything in return. Of course if your playing Horde Orks your going to like that ability even less.....
Amusingly enough only one has a specific anti-daemon ability and that's the Banisher. Any Daemon within 6" of him must re-roll their invulnerable saves. Mildly irritating, but when your saves that bad anyway hardly game breaking.
I'm going to lump Grey Knight Strike squads and Interceptor Squads together as they have the same annoying ability.....No not Hammerhand.....
Warp Quake - This is the one that's going to cause Daemon players the most problems. Any items of war-gear that prevent Deep Strike scatter stop working within 12" of the squad using this power. For those Chaos Space Marine players that use Lesser Daemons that means they are destroyed as they have to have an Icon to appear from. Actual Daemon Codex : Daemons will lose the effect of any over pointed Icons that they paid for but that's not the worst of it.....
Any enemy unit deploying by Deep Strike (so everything Daemons have) within 12" of the squad (after scattering) will automatically suffer a deep strike mishap.....Not scared?
Well you should be,
A model can be two inches away from another one and still be in coherency and a base is as near as dammit an inch across. This means at maximum spread a 10 man Grey Knight Strike or Interceptor Squad can create a 52" by 25" zone of doom for Daemons that will kill them 33% of the time, send them back into reserve 33% of the time and at best will allow the Grey Knight player to put them wherever he damn well pleases the other 33% of the time.
Despite what my 'state of the art' blog might indicate to the contrary I'm actually old school and also don't have CAD so here's a drawing to illustrate my point.....
If any of you out there would like to do a CAD version and e-mail it to me it would be much appreciated ;-)
Obviously that's an extreme example but in Dawn of War deployment you could do that twice and if you have a HQ with Grand Strategy to give them Scout you could potentially do it with 3 different units.....Not quite an 'auto-win' button but not far off....
I've already mentioned the Dark Excommunication ability in conjunction with Librarians but unfortunately Nemesis Dreadknights get it as well. This effectively means that the Daemon units that will be best at destroying Dreadknights will be doing it using their basic profile 91.67% of the time. So they'll be getting their 2+ save against anything without monstrous creature status and those monstrous creatures will be losing many of their upgrades including such useful things as Unholy Might.
I think that's everything covered.
It's looking less and less good for the forces of evil now isn't it.....
Thoughts and Comments are (as usual) most welcome.
You have read this article Chaos Daemons / Grey Knights / Tactica with the title Killing Grey Knights with Daemons - Part 2 (b): Anti-Daemon Psychic Powers. You can bookmark this page URL http://llourenzzo-putta.blogspot.com/2011/04/killing-grey-knights-with-daemons-part_6.html. Thanks!