Detachment question

Hello all. My apologies for the silly question but I want to make sure that I understand how to do this. Say I want to include Deathwatch with my Sisters. I would have to fulfill the requirements of a detachment for each correct? Now how does it work if instead of a detachment of Deathwatch I want to include Sisters of Silence or an Assassin instead? How would that work? Thanks in advance for the help.

each detachment that you include must have one faction keyword in common. e.g IMPERIAL... (so you could include a detachment with all three Deathwatch, Sisters and an assassin in e.g. a Battallion Detachment)

however the way is is set up (and similar to AoS) is the more focused you go the better the: warlord traits, Relics, special rules etc. (at least that seems what will happen when the codexes actually drop, not just the faction rules).

so at the moment as an AdMech Player I could take a mostly ADMech Army with a couple of other IMPERIAL units (e.g. assassin, SM Tac Squad etc.) however I will only gain the Canticles of the Omnissiah rules (gives things like reroll 1's to hit, or cover for the whole army for one turn) if I take a pure AdMech list.


if you wish to you could take a detachment of pure Deathwatch (e.g. Batallion, +3 Command Points), then (from pg 245 of the main rulebook) you could take an Auxilliary Support Detachment (basically giving you one unit which can be elites, troops, HQ etc.) from a different faction (e.g. Assassins) for the low cost of -1 Command Point per Aux Support Detachment.

if you wish to go for more than one unit from another faction take a separate Patrol detachment for that faction instead, so as to avoid the negative command point penalties.

Thank you so much for the reply and explanation. It's truly appreciated.