Spells that force your opponent to mill half their library are common for mill decks, but for it to be an additional cost isn't quite so common
While you can do some weird stuff with this and Food Chain, the common use case is saving your haymaker from Swords to Plowshares, which is honestly pretty sick
These are the most coveted largely because they're the most powerful cards in the game
I am speaking about Relentless Assault effects that give you another combat step, another token and note that the tokens don't die until your end step, so you can get two attacks in with the first token copy
Just saying "use an app" isn't helpful advice in and of itself (which ones?), and "use a trading app" doesn't mean the app will have any translation capacity available
I had to reread this twice to make sure the trigger really does say each player