Rift Herald

Rift Herald is an interesting card. Usually, we don’t print effects like Rift Herald’s Deathknell that don’t say “may.” However, even without the “may,” an important principle that we want to hold for Riftbound is that game effects cannot force a player to perform a game action on an object with specific characteristics whose information status is private.

Imagine if we lived in such a world. When Rift Herald’s Deathknell resolves, your opponent claims to not have a unit in their hand. But what if they do have a unit and they want to try to save it for a more opportune moment? What if playing it would be actively detrimental to them? Suddenly, every time your opponent says they don’t have a card to play that matches the appropriate characteristics it makes you wonder if they’re lying to you. How do you hold them accountable? Do you go over and look at their hand? Do you call a friend to check their hand? If you’re at a tournament, do you call a judge? This is an unsustainable level of paranoia to subject players to. We don’t want that and neither do you.

The following rule will be added in the next rules update and will go into effect now:

A player cannot be compelled to perform an action on cards whose privacy is secret or private if that action specifies a type or quality of card. If an effect would compel a player to perform an action on cards whose privacy is secret or private, and if that effect specifies a type or quality of card, the player in question may ignore it instead.

Source : Riftbound: Unleashed Rules FAQ and Clarifications