Of course, this means you need a character on board that can initiate the challenge before Maid Marian gets value, but there are 11 4-cost characters that all have decent Strength values, so it isn't hard to get something down the previous turn that can take the Challenge
With even normal Enchanted Rare cards only estimated to appear in roughly one in 100 booster packs, finding an Enchanted Rare Discard card is like hitting the jackpot in the lottery by comparison
There are 49 inkable and 11 non-inkable cards
Vivi Ornitier's last ability resolves before the spell that caused it to trigger
Boost is the new set mechanic that allows a player to put a card from the top of their deck under a character to give them powerful passive abilities
You'll find a mix of commons, uncommons, rares, and foils, giving you plenty of options for deck-building