Mirrorshell Crab
Artifact Creature — Crab
Ward 
(Whenever this creature becomes the target of a spell or ability an opponent controls, counter it unless that player pays .)
Channel — 
, Discard this card: Counter target spell or ability unless its controller pays .
Cristi Balanescu
Rulings
If a channel ability requires a target, you may not activate it without a target just to discard the card.
(wotc • 2022-02-18)
Discarding the card is part of the cost to activate a channel ability.
(wotc • 2022-02-18)
If a player casts a spell that targets multiple permanents their opponent controls with ward, each of those ward abilities will trigger. If that player doesn't pay for all of them, the spell will be countered.
(wotc • 2022-02-18)
Rulings
If a channel ability requires a target, you may not activate it without a target just to discard the card.
(wotc • 2022-02-18)
Discarding the card is part of the cost to activate a channel ability.
(wotc • 2022-02-18)
If a player casts a spell that targets multiple permanents their opponent controls with ward, each of those ward abilities will trigger. If that player doesn't pay for all of them, the spell will be countered.
(wotc • 2022-02-18)