Grand Master Voldus, Warden of the Librarius

A unit that contains at least one model with this special rule re-rolls results of 1 when making Deny the Witch tests.

Grey Knights Psykers can generate psychic powers from the Daemonology (Sanctic) discipline.  In addition, unless otherwise stated, when attempting to manifest psychic powers from the Daemonology discipline, Grey Knights Psykers only suffer Perils of the Warp if two or more 6s are rolled when taking a psychic test.

Deep Strike Mishap Table: D6 Roll

1: Terrible Accident! - The entire unit is destroyed!

2-3: Misplaced - Your opponent may deploy the unit anywhere on the table (excluding impassable terrain, but including difficult terrain, which of course counts as dangerous for Deep Striking units), in a valid Deep Strike formation, without rolling for scatter. Units embarked on a misplaced Transport can disembark during their Movement phase as normal.

4-6: Delayed - The unit is placed in Ongoing Reserves.

Bulky models count as two models for the purposes of Transport Capacity.

Relentless models can shoot with Heavy, Salvo or Ordnance weapons, counting as stationary, even if they moved in the previous Movement phase. They are also allowed to charge in the same turn they fire Heavy, Ordnance, Rapid Fire or Salvo weapons.

A unit that contains at least one model with this special rule automatically passes Fear and Regroup tests. When it Regroups, the unit does not make the 3" Regroup move, but can instead move, shoot (or Run) and declare charges normally in that turn. Furthermore, if a unit containing one or more models with this special rule is caught by a Sweeping Advance, they are not destroyed, but remain locked in combat instead.

Independent characters can join other units.  They cannot, however, join units that contain vehicles or Monstrous Creatures.  They can join other Independent Characters, though, to form a powerful multi-character unit!  Independent Characters pass Look Out, Sir rolls on a 2+. A unit that contains one or more Independent Characters does not need a double 1 to Regroup if reduced to below 25% of its starting numbres, but instead tests as if it had at least 25% remaining.

Full details in BRB. Rule too long to copy verbatim.

This rule is often presented as Preferred Enemy (X) where X identifies a specific type of foe. If the special rule does not specify a type of foe, then everyone is a Preferred Enemy of the unit. A unit that contains at least one model with this special rule re-rolls failed To Hit and To Wound rolls of 1 if attacking its Preferred Enemy. This applies both to shooting and close combat attacks.

A model with this special rule is a Psyker. This rule is typically presented with a Mastery level, shown in brackets - if no Mastery Level is shown then the model has a Mastery Level of 1. Rules for generating and manifesting psychic powers can be found in the Psychic phase section.