1 Secluded Steppe
(However, if you treat some of these as wincon, you should keep those) As I mentioned, Im not quite sure what is common to play with Sythis, but as you have many spells with mana cost 3 or less, you could try Sun Titan
That's because when it's exerted, it gives every other character on your board +2 strength
While Necrodominance is on the battlefield under your control, abilities that trigger whenever a permanent you own is put into your graveyard from the battlefield (for example, "When this creature dies") won't trigger because cards and tokens are never put into your graveyard
Effects that end the turn like Time Stop and Obeka, Brute Chronologist are fun because we dont see them terribly often
That borders on a sweeper in the right deck