Disciple of Phenax

When this creature enters, target player reveals a number of cards from their hand equal to your devotion to black. You choose one of them. That player discards that card. (Each {B} in the mana costs of permanents you control counts toward your devotion to black.)

From Magic: The Gathering.

Open the interactive version on https://mythscribe.cloud/app/tcg/cards/cms6oc7z78elvpb1h0wfmmh9u.