mtg rivals of ixalan booster box Magic: The Gathering and you will wield the planes greatest power Ixalan - Prerelease Pack :

Commander Filler The final four cards are mostly Commander filler cards at this point, though a couple are quite strong in that role

Cid, Freeflier Pilot* Cheap cost reduction, with jumping and limited recursion make this Cid a definite win for vehicle and equipment decks, as Final Fantasy s premiere pilot and mechanic is ready to get to work

Crystals The full colored cycle of Crystals reduce costs, and each one has a static ability and an activated ability, so the 4 mana value slot is a key one to launch you into the the biggest and strongest cards, and rely on 2-mana rocks to curve into these on turn 3

Then there is this much longer video where Magic: The Gathering designers Gavin Verhey and Zakeel Gordon chat with host Blake Rasmussen about the cards