You see, Vintage is a special format where (almost) all cards from Magics history can be played in some form or another
Alongside mainline sets, Bandai frequently releases highly competitive Starter Decks, Ultra Decks, and special premium collections
it includes the most recent card sets and is played at Pokmon Leagues and Championships
Note that if it was forked, you cannot win with it, as that won't count as "casting," but something that casts it for free from a non-hand source will count the first time, so something like Golos, Tireless Pilgrim can count as the first time you cast it, and net you seven life and stack it seven down
I think this card may be interesting alongside some sort of untap synergy with a card like Filigree Sages
There are graveyard decks that mill their own library, but these are rarely described as "mill decks." There is also some disagreement about whether decks that mill their opponents for value, like UB Rogues, count as "true" mill decks