Examples of popular cards in Modern include Silent Arbiter and Aetherling
Put simply, its a value engine that also can close out a game, and a cheap one at that - sitting at less than $2, this is at an all-time low, down from a historic high of just over $16 about two years ago, no doubt thanks to a slew of reprints
Anyway, this is something you should pretty much never main deck, but not too terrible if you go up against an opponent with enough targets
Here is an example of a complete Main Deck for Puresworns
Cannot be targeted for attacks and is unaffected by other cards' effects while you control a face-up "Distortion World"
Each reward pack also includes a QR code you can scan to reset the game, making it easy to teach someone else