From just increasing availability of powerful cards to all the sweet new alternate art, Double Masters will have an immediate impact on your Commander environment
Long-game card-drawing advantage aside, Kefnet comes down early and, if set up properly, can deter people from attacking you for a good chunk of the game
Moogles' Valor BPhillipYork: If this was cheap it would be amazing
(Treat it and anything attached to it as though they don't exist until your next turn.) Whenever King of the Oathbreakers or another Spirit you control phases in, create a tapped 1/1 white Spirit creature token with flying
Each of the four Commander Decks comes with a scheme deck (including some schemes new with this release) that you can use to strike fear into the hearts of your opponents
Since Ashnod's CouponAshnod's Coupon and R&D's Secret LairR&D's Secret Lair are now technically banned in a Constructed format, she can assemble that nasty combo