Many cards in Whispers in the Well have this mechanic, which allows a player to pay an extra ink cost to tuck a card under your character and activate a new, more powerful ability
Enter your friend's email address associated with their MTG Arena account or MTG Arena username (including the 5 digits after their username, e.g
Starm requires building around, but he doesn't necessarily have to cost a lot of money - because they're ordinarily so underwhelming, spells and creatures that can deal exactly one point of damage are very cheap, and Starm triples their output
However, the payoff is huge
And that, my faithful readers, is just bad design
The most obvious answer beyond that was seeing what rare or mythic rare you opened, or if you found that key uncommon or common for your deck