In your Shooting phase, when a friendly Adeptus Astartes Transport unit has shot, you can select one enemy unit hit by those attacks. That enemy unit is assailed until the end of the turn.
While a unit is assailed, when an Adeptus Astartes unit that disembarked this turn targets that unit, those attacks have [Sustained Hits 1].
Enhancements
Damocles-class Uplink
Captain model only. In your Movement phase, if this unit is embarked within a Transport unit, you can select one friendly Adeptus Astartes Infantry unit within 6" of that Transport unit and select one combat doctrine. That combat doctrine is active for that Infantry unit.
+15
Linebreaker Onslaught
Adeptus Astartes Infantry model only. If this unit disembarked this turn:
-This unit can re-roll charge rolls.
-Enemy units cannot target this unit with snap shooting attacks.