The new mechanic that most intrigues me is the multikicker-esque one found on Bloodthirsty Adversary, Intrepid Adversary, Primal Adversary, Spectral Adversary, and Tainted Adversary
Spectacular Spider-Man (Various) The Spectacular Spider-Man cards from this set were bound to be popular, both because the card is great and its artwork is awesome, but if you have a textured foil one, you might be in for a windfall
The secondary commanders are the two other legendary creatures that share the primary commanders color identity
In the case of Kit Cloudkicker, Navigator, the player may play this card on top of another card named Kit Cloudkicker at half its usual asking price - or just three ink
Although it only works for one round, it can effectively prevent players who have a card in play that gives them a substantial amount of lore, or perhaps can even come in clutch at the end turns of a game
On entering the battlefield, this black legendary enchantment gives all creatures -X/-X, where X equals the amount of extra mana paid into the enchantment