I wish to add Grey Knights as allies to my harlequin army need some advice :(

[Xaric]

Okay so to give you a picture of what I am bringing here's my list so far.

Troupe 5 man squad
+Fusion Pistol and Harlequin's Caress
Death Jester
Shadowseer
+Neuro Disruptor

Troupe 5 man squad
+Neuro Disruptor and Harlequin's Kiss
Death Jester
Shadowseer
+Neuro Disruptor

Troupe 5 man squad
+Shuriken pistol and Harlequin's Embrace
Death Jester
Shadowseer
+Neuro Disruptor

Solitaire

Skyweaver 2 man squad
+Zephyrglaive

Skyweaver 2 man squad
+Haywire cannon

Voidweaver
+Prismatic cannon

(1345 points)

Now I normally play 2000 point games and this is going to be a elite army so low model count now I want to add some grey knights for fluff reasons a custom sort of alliance between a small brotherhood of grey knights that seem to always bump into these harlequins as they mostly hunt daemons.

Now my question is what to take with the grey knight faction to give it that added bonus to make it viable I need range and psyker powers hence why I am choosing grey knights as the allied factor but I don't know much about what is good or bad with grey knights other then the big robot that sets everyone on fire :D

[Reldane]

Grey Knights armies pretty much build themselves. the only HQ that is remotely takable is the Libarian, so you take that. troops you take terminators, because the other option is extreemly expensive power armoured marines who don't have specail guns that they can move and fire (2 shots at range 12" is not a good use of a psycannon). this is doubly true if you want to keep your army elite heavy low model count.

by taking the grey knight detachment, you only need one troops same as an allied detachment, but it gives you deep strike ariving from turn 1 and mulitple slots for elites, fast attack and heavy support.

for heavy support take the dreadknight (remember that each dreadknight requires 3 psychic dice to impove their invunrable save each turn), the jump pack is a good look for it, and it is worth giving it either the hammer or the sword else it doesn't have a forceweapon. the guns are all takeable but the torrented incinerators are very good for making a mess of things.

fast attack is just two units and personally I have never seen interceptors do anything worth taking them for. the Stormraven is pretty solid however and is the only thing that can shoot up in the army (I don't personally like it so I can't really give you much advice on it however).

for elites purifiers. they are most importantly warp charge 2 and have cleansing flame but they are expenisve and die just as easily as a tactical marine. in combat they are certainly good, however might still strugle into hordes. I would generally advise 1 hammer, 2 halberds and 2 falchions, I think the knight of the flame can take melta bombs, if he can give the hammer to someone else as they all have 2 attacks.

things not to take under any circumstance: techmarine (1 wound hq for nearly the same as the libarian?), brotherhood champion (costing more than a chapter master but without the attacks, wounds or upgrade options) dreadnaughts (costing 1 mastery level at 25pts seems fair, but as they only get sactuary to give themselves a 6++ it really doesn't seem worth the cost). Psilencers (yes they have force, no they still don't inflict unsaved wounds. they are bad.) Mordrak (you can't him and his ghost knights have gone :( maybe next time) Crowe (he is a brotherhood champion except even more expensive, he doesn't have armour pen except in a challange so even cultists are getting saves vs his attacks (once the champion is dead), he doesn't make purifiers troops)

[son_of_volmer]

My go-to Greyknight allies are:

level 3 Librarian with Domina Liber Daemonica (you can have four chances to generate you preferred Santic powers)
5 man Terminator squad with plain swords and an incinerator
5 Purifiers no upgrades (shoot Cleansing Flame during the psychic phase and then run in the shooting phase)
5 Purgators 4 incinerators (4 flame templates!)

You could take a squad of Purgators with 2 Psycannons and put them in a Rhino and have them shooting from the fire points, but the range of the Psycannon isn't great.

A Dreadknight would be sweet but upgrading it becomes expensive.

[Xaric]

Sounds good but GK terminator librarian is sold out :(

[Reldane]

there isn't a grey knight specific libarian, they just don't seem to have put the new plastic terminator libarian on the grey knights page. just search up the standard space marine version. also remember the stormbolter is an upgrade (standard he has no guns) when deciding how to build your model.

on other notes; why does it have the techmarine with servitors on the grey knights page seeing as the grey knights techmarine doesn't get the option of any servitors.

edit: on notes of powers for the libarian, he will have to be in a unit of grey knights due to not being battle brothers with eldar, so try to decided what unit he will be in before you decide what dicipline to take. if he is with a unit of purifiers and rolls hammer hand and cleansing flame, he has rolled two dead powers, as the unit can only cast any psychic power once per turn.

[Xaric]

I have a crazy idea with the librarian sticking him with paladins and deep striking the hole allied detachment in Grey knight fashion and using there nova ability's because of harlequins speed to get into combat :D but I am unsure as they would be classed as enemy units due to allies of convenience? thus be affected by the nova powers wile in combat with the enemy unit? because it does say cant be targeted by psychic powers?