At the beginning of each opponent's upkeep, if that player has one or fewer cards in hand, they lose 3 life.
Shrieking Affliction’s ability will trigger only if an opponent begins their upkeep with one or fewer cards in hand. The ability will check the number of cards in that player’s hand again when it tries to resolve. If that player has two or more cards in hand at that time, that player won’t lose life.