Once we've amassed an army of Devils, we use them for various nefarious purposes, sacrificing them for mana to Ashnod's Altar or turning them into lethal threats with cards like Torbran, Thane of Red Fell
If a player is in a dungeon, you'll see it on the left side of the screen, next to their emblems and other game effects
Legality depends on the tournament format -- Year-End Review can be legal in some formats and banned or restricted in others
(To scry 3, look at the top three cards of your library, then put any number of them on the bottom of your library and the rest on top in any order.) You might also be interested in these products
Combined with its very limited pull rate, this treatment has made it the definitive chase card of the set, a blend of raw competitive power and high-end collector appeal that few other cards can match.
That seems to have changed in the past few years, though