Swinging with a 20 power Trample creature on turn three is no joke, and can absolutely end the game if your opponent is off to a slow start
Not the strongest of removal spells, but Self-Destruct is great at sacrificing a creature thats already about to die, and you might even have some fun with Jumbo Cactuar
(12/7/2018) You may cast a sorcery this way even if it's not your turn
Additionally, many of these decks, including this one, will have proliferate effects which can let Gatewatch Beacon have extra loyalty counters to give away giving even more bang for your buck
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
1: Rebellious Renegades 4 cards sAnS mERcY 6 cards Hatsune Miku: Sakura Superstar 14 cards Fallout: Vault Boy 9 cards Fallout: Points of Interest 11 cards Fallout: S.P.E.C.I.A.L