This card is an iteration of Ragavan, Nimble Pilferer , a legendary creature that, whenever it deals combat damage, creates a treasure token and exiles the top card from your opponent's library, allowing you to play it until the end of your turn
The MTG card count increases multiple times per year with each new release
This means that, for example, you can't activate an equip ability between combats.
On the other hand, a high cmc deck that wants to win on turns 10+ will want a higher land count so you can consistently hit your land drops on turns 5+
Play With Fire will do more in other formats, but it will definitely find a home in EDH
The flashback on Memory Deluge isnt just free flashback value instead of looking at four cards, you get to look at seven