It gives a huge advantage with mulligans, especially with the new London Mulligan First hand, you've seen 7 cards + 5 OUAT Second hand, you've seen 14 cards + 5 OUAT Third hand, you've seen 21 cards + 5 OUAT Once Upon a Time serves as the missing link in whatever you need during mulligans
If they want to retreat their injured ex to the bench or are trying to set up and evolve, with Boss's Orders, you can just say no and manipulate their board
Then, rip the card you believe is fake
You have to understand theyre in this to make money so you probably wont get top dollar for your cards
You really need to get through Tomb of Annihilation for the Archlich to be useful, but it can be a real problem for your opponents once you do
Once per turn, when a "Dark Elf" monster you control declares an attack, your opponent loses 1000 LP