Editing Warhammer 40,000/8th Edition Tactics/Grey Knights (section)

===Sanctic Discipline===
Values in parentheses are odds of success base, then with Brotherhood of Psykers up.

#'''Purge Soul:''' WC 5 (83.33%,91.67%). When manifested, pick an enemy unit within 12". Have a 1d6 roll-off and add your respective Ld. If the target rolls equal to or higher, nothing happens. If the caster rolls higher, the target unit suffers a number of mortal wounds equal to the difference.  
#*Note: Purge Soul is can do well as its one of your few targeting.  If you take you should also be doing combos to widen the Ld difference. with the +1 leadership banner and the +1 leadership warlord trait, and it's actually helpful against vehicles/monsters or single models with a really high toughness value.
#**Bring along everyone's favorite Madonna Impersonating Inquisitor, Greyfax, in a Min Strength Vanguard and she'll share her Ld 10 with you boosting your base to 12 with the WL trait and Ancient's Banner. She also brings Terrify to reduce a target of choice within 18" by 1 Ld in addition to turning off their overwatch. The biggest problem is this forces you to either footslog your whole blob for maximum effect or pay for a transport for her. Lord Hector Can Teleport in with the boys for just 30 points more and is a better Psyker but doesn't help your own leadership as he's only Ld9 himself. Note: the inquisitors Unquestionable Wisdom allows you to use their ld, which overrides your leadership stat, thus buffs to your own ld from the banner do not stack as they modify your stat, which is them overwritten by unquestioning loyalty. Greyfax has a fixed warlord trait so caps out at 10, which you get from a banner anyway.
#'''Gate of Infinity:''' WC 6 (72.22%,83.33%). Pick a friendly {{W40kKeyword|GREY KNIGHTS}} unit within 12" of the caster. The unit may immediately re-deploy anywhere on the battlefield more than 9" away from an enemy unit. Yes, you read it right, it doesn't say "{{W40kKeyword|GREY KNIGHTS}} {{W40kKeyword|infantry}} unit", just "unit"; SAY HELLO TO MY LAND RAIDER CRUSADER AT RAPID FIRE RANGE ON TURN 1!!! That's 24 shots minimum, not counting the storm bolter, multi-melta, etc. The only flaw is that you can only attempt to cast on per turn with so many good targets. Think about what needs it more and don't let it get dispelled.
#*This power right here. With a slightly clever setup, you can toss your LR around the board like some rabbit on speed, popping where it must go the moment it is needed. Also, nothing hinders you from teleporting out of melee. Your termies are tarpitted where you do not want them? No problem, just zip away. Also, this won't hinder you from shooting or charging, as the Fall Back move would.
#'''Hammerhand:''' WC 6 (72.22%,83.33%). Pick a friendly {{W40kKeyword|GREY KNIGHTS}} unit within 12" of the caster. Add 1 to their wound rolls in melee. Basically, you can wound anything on 5's. ANYTHING.
#*This buff is better the worse the target's ability to wound was to begin with, so if you're using it, definitely try to stick to Falchions over Halberds, if you weren't already. Or cast it on a Dreadknight and wound on 2+.
#'''Sanctuary:''' WC 6 (72.22%,83.33%). Pick a friendly {{W40kKeyword|GREY KNIGHTS}} unit within 12" of the caster. It gets 5++, or, if it already has an invulnerable save, adds 1 to it, to a maximum of 3++ (i.e. it won't stack with Warding Staffs on a 4++ model because GK players can't have nice things). Lasts until your next Psychic phase.
#* Best used on Grand Master Dreadknights or Warding Stave multi-model units wearing Terminator armour, for a 3++ on an already hard target.
#'''Astral Aim:''' WC 5 (83.33%,91.67%). Pick a friendly {{W40kKeyword|GREY KNIGHTS}} unit within 18" of the caster. Until your next psychic phase, the unit is able to target enemy units they cannot see during the shooting phase, and units they target do not get any cover bonuses. Use this to thwart Ork boyz who think they're being clever by declaring a charge against you from around a building, or destroy cover-camping assholes like T'au or Imperial Guard infantry. Of course, one of the greatest uses is to stick a shooty Dreadnought behind a wall out of line-of-sight the whole game, allowing him to pump out shots in safety without worrying over firing lanes.
#'''Vortex of Doom:''' WC 8 (41.67%,58.33%). If manifested, a vortex opens above the nearest visible enemy model within 12"; that model's unit, and every other within 3" of that model, suffers d3 mortal wounds (d6 if cast on 12+).
#*Expected mortal wounds for only one target unit are 0.875 without BoP, 1.29 with; since you can't target the power, this only gets up to really useful levels in melee with multiple small units, to ensure a lot of targets are close to each other and to you. (Edit: Absolutely DO NOT cast Vortex in melee EVER. Since the wording of the power is "...and every other unit within 3 inches" (not specifying whether friendly or enemy) this means vortex will affect your own units as well.)
#* Pro tip: Combo with Psychic channeling and Empyric Surge stratagems to try and stack the deck in favor of getting 12+ (a roll of an 11+ because of Grey Knight bonus). Use this on MSU Tau fire warrior gunlines and you're laughing.

In short: what should be the discipline of the best psyker army of the Imperium ends up being just mediocre. Of your six powers, two will practically always be used by the same unit (Sanctuary for Grandmaster Dreadknights, Astral Aim for Purgation squads or Venerable Dreadnoughts), one is too unreliable (Purge Soul) and one too situational (Vortex of Doom). The only two that you'll ever need to consider using tactically are Gate of Infinity and Hammerhand. Just more salt in the wound.

Alternate take: Mediocre? This list is rife with dorito finger level That Guy cheese.

Vortex of Doom is situational yes, but the beautiful thing is if the situation EVER comes up anywhere on the board, you're playing an entire army of deep-striking, re-deploying psykers. Since you can redeploy up to two units (Interceptors with Stratagem & GoI), you can punish an opponent who doesn't keep his things close together by placing your dudes in areas where his units can be attacked without your dudes being subject to any volume of fire from other units. This can lead to a situation where he ignores your teleporters blowing up vulnerable spots until he sends armour away from better objectives to hunt them down, at which point they can simply teleport away again. If he accounts for this and deep strike by clustering his units, it's Vortex time.
Even if you take Vortex and your opponents spreads all of his things awkwardly to disrupt his army placement, to never give you a context to use it, that's good in my books, go back to harassing spread out heavy weapon infantry stragglers.

If you find purge and vortex are underpowered, just throw them on the spell hungry Voldus, letting the rest of your army use the bread and butter spells. Smite Lite, Purge Soul, and Vortex coming from the same dude, you'll probably get SOMETHING going for you. And when the dice gods DO smile upon you, you shall be most pleased when Voldus mangles an entire elite squad, or two, locking a third thing melee (if not also crushing it.) I have had Voldus pull this off with these lamer spells a few times, and it is glorious (if he doesn't just teleport away after deep striking in).

The cheese you can blast when you are the only man in the Imperium (who isn't a vegetable) who can cast three spells at once