Cards are further enclosed in a paper receipt, inside a standard envelope
In the case of Keruga, the companion requirement is that your starting deck contains only cards with a mana value of three or greater and lands
Hades forces your opponent to make an impossible choice: let you get vital resources to your hand in the form of drawing two cards, or send their precious character to the bottom of their deck
While it does help us get up to 27 or 30 life to turn on our payoffs, and it is a "free" way to trigger Ajani's Pridemate and Heliod, Sun-Crowned, being colorless is a big downside and occasionally forces us to play things off-curve (especially Linden, the Steadfast Queen, with its triple-white-mana cost)
The Van Gogh Museum later told me that it had enough treasure hunt leaflets (in Dutch and English) to last until the end of the collaboration, but thats not what I found
How does that happen