Not only does this look like the best commander for the Necrons deck itself, it seems really sweet to build your own deck around and really focus on trying to trigger the first ability as often as possible
There's already fairly high upside reanimating an opponent's creature at instant speed, but you can eek even more value out of Conscription by firing it off in response to an opposing reanimation effect
The creature only enters tapped and attacking
Whenever one or more other creatures you control enter, if one or more of them entered from a graveyard or was cast from a graveyard, put a +1/+1 counter on each creature you control.
#5: Reflector Mage It's possible that Reflector Mage should be higher on our list because it's absolutely absurd with Naban, Dean of Iteration in any sort of creature matchup, but the fact that Modern has a reasonable number of creature-free control and combo decks where the combo of Naban and Reflector Mage is pretty bad keeps it in the middle of the pack
A common trick is to give a creature first strike after blockers have been declared, but before the first combat damage step