Grey Knight codex gotchas, or, So you've decided to play against Grey Knights

Heres my summary of a nice summary of strange GK codex parts that will trip people up

Grey Knight Special Rules, all Grey Knights have these

Fearless - all Grey Knights are Fearless, using the main rule book version of the rule

True Grit - GK storm bolters count as close combat weapons providing they have not charged in the same Assault phase. This means they get +1A for dual wielding, but not on the turn they charge, essentially removing their +1A for charging.

The Aegis - Any time an enemy uses a power that requires a psychic test vs a grey knight squad or character, the GK unit can resist the power by rolling a D6 + highest unit leadership versus D6 + attacker model leadership. If the GK ties or gets higher, the power has no effect.

The Shrouding - Each time an enemy unit fires at a GK unit they must check if they are within 3 * 3D6 inches. If they're out of this distance, the firing unit cannot fire at an alternate unit instead. Ordnance weapons fire as normal but double their scatter distance if they fall outside the spotting range. Night fighting skills and equipment have no effect on this, but units including a psyker can reroll the dice and accept the second result instead. Actual night fighting rules override this rule completely.

Rites of Exorcism - Daemons attempting to charge Grey Knights must roll dice for their Assault range as if they were moving in difficult ground. Because daemons assaulting Grey Knights units are required to take a difficult terrain test when assaulting, they will fight at Initiative 1 in the first round of close combat (unless they have assault grenades -- like frag grenades -- or their equivalent)

Other Grey Knight and DH rules

Retinues - A Daemonhunter with retinue does not have the Independent Character rule until the retinue is gone, so cannot be singled out in close combat until he runs out of meat shields.

Psykers - While technically all Grey Knights are psykers, only the squad leader (Justicar, Brother-Captain, Hero) counts as a Psyker on the board, for it is through them that all psychic powers of the squad are channeled, and from there all ranges are measured and tests taken.

'Daemons' - Many GK rules refer to Daemons, and this refers to the following units: All Daemonhosts, Greater Daemons and Daemon Packs, Daemon Beasts, Nurglings, Daemonically Possessed Vehicles (such as Defilers, Parasitic Possession, Living Vehicle, Mutated Hull), Eldar Avatars, Possessed Chaos Space Marines, and Chaos Lords with the Daemonic Stature gift or over 50 points of daemonic gifts.

Vehicle differences - Daemonhunter codex vehicles include the Rhino, Chimera, Land Raider, and Dreadnought, but these vary quite a bit from their SM and IG codex counterparts. In most cases, the DH vehicles are worse: fewer fire points, less free wargear, smaller carry capacity, fewer weapons. In some cases they are better, the DH dreadnought is cheaper, and the DH land raider crusader is the best in the game. Aside from their loadouts and price, here are some key vehicle rule differences:

DH assault cannon is heavy 3 (SM assault cannon is heavy 4)

DH hurricane bolters can fire regardless of how far the tank moved and what else is firing, this means you can move a full 12" and fire both hurricane bolters and 1 other weapon (from power of the machine spirit)

DH dedicated transports are truly locked to their unit, while other transports can take any ally. Only Inquisitorial forces (non GKs) have access to dedicated transports.

GK land raiders comes with power of the machine spirit, but the inquisitor's dedicated transport land raider does not

Smoke launchers - Reduce all penetrating hits to glancing hits, cannot shoot in the same turn smoke is popped

Dozer blades only work when moving 6" or less

Wargear rule gotchas - these are some big big differences between DH rules and main rule book rules or SM/IG codex rules that your opponent should be told before starting, or there will be an argument and lots of codex flipping!

DH psychic hoods have infinite range!

DH force weapons (including nemesis force weapons) do not cause instant death, they cause the model to be slain outright, that means in will kill any model normally 'immune to instant death'! Only a GK Grand Master's NFW counts as a Force Weapon, and only an Inquisitor can purchase one as an upgrade.

Psycannons, bolters firing psycannon bolts, and incinerators ignore invulnerable saves. Cover saves and armor saves may be taken. Models whose save "is invulnerable" are affected as well, including dodgy assassin creatures whose invulnerable save represents their agility.

DH storm shield is only 4+ and only vs wounds from one model (SM storm shields are an overall 3+ invulnerable). DH storm shields however count as CCWs and will let you dual wield if paired with something other than a thunder hammer.

DH thunder hammers inflicting a wound on a model cause the model to be unable to attack until the end of its next assault phase, meaning a model can potentially never attack if it keeps getting whacked by a DH thunder hammer. DH thunder hammers that hit a vehicle cause a crew shaken result without having to glance and penetrate like SM thunder hammers.

Allies

DH armies can certain IG or SM units, but not both at once

DH armies with Grey Knights cannot take allied space marines

SM/IG/Sisters armies can take DH as allies, including using Grey Knights, this is the only time Grey Knights can be on the same army as Space Marines. The host army must have its 1 HQ & 2 Troops before taking any allies. Daemonhunters cannot ally with any force that already has allies, except for 'separate detachments' and units from other forces of the Inquisition (witch hunters, alien hunters).

No DH Heavy Support units may be taken when including Daemonhunters as allies! And since only the Inquisition has access to dedicated transports, this means that allied Grey Knights will have no access to DH codex vehicles, even GK dreadnoughts. They can ride in the host army's transports, but cannot start the game in them.

Useless rules - DH rules that are now null and void due to the main rulebook changing

DH Teleport Homers are useless because deep striking does not use templates

DH Psychic power Banishment is no longer valid

GK first half of special rule Rites of Exorcism is not valid because daemons do not take instability tests anymore

GK special rule Daemonic Infestation is not valid because there is no longer a Sustained Attack rule, except when referring to the Daemons available to your opponent from the DH codex.