You choose which exiled adventurer card, if any, to put into that player's graveyard after seeing their hand
This pricing is consistent with previous Secret Lair releases
Doubling effects are highly dangerous, because now every pump spell does double damage, and there may even be other things that can double the effect again
As sets rotate out of production, their foils will rise in price as the cards become rarer
For those unfamiliar with Archenemy, it is a format in which three players join forces and face off against a fourth, who takes the role of a "final boss" type figure for the other players to attempt to defeat
Twenty cards is certainly not a high barrier in formats with fetch lands and cheap spells, but it just appears to be too bad before that period to be worth running, at least in a playset