Jensus Natorian

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.

The Mission Tactics special rule represents the unique way in which the Deathwatch go to war.  At the start of your first turn, pick one of the Mission Tactics.  It will remain active for the entire battle unless you decide to change it as described below.  As long as the Tactic is active, it affects all units in your army that have the Mission Tactics special rule.                                           
                                                                                                                                                             
Once during the battle, at the start of any turn after the first, you can choose to change the current Mission Tactic to another one.