Collector Boosters are the best way to collect variant rares and mythic rares, as well as foil cards, and they're the only place to collect foil-etched, extended-art, and neon ink cards
As you should know by now, the targets of spells and abilities pass the legality check twice: first time when casting/activating/placing them onto the stack, and another time upon resolution
Shefet Dunes Shefet Dunes costs nearly nothing to put in most white decks because it can just replace a basic Plains
It's ok to lose here, too
Prototype Prototype is a new ability found on several artifact creature cards representing the machines of war in two very different stages of development
Heavy green decks may play this as an Explosive Vegetation variant that does something later in the game