Eiganjo, Seat of the Empire

{T}: Add {W}.
Channel — {2}{W}, Discard Eiganjo, Seat of the Empire: It deals 4 damage to target attacking or blocking creature. This ability costs {1} less to activate for each legendary creature you control.

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Kamigawa: Neon Dynasty Promos

Kamigawa: Neon Dynasty

Discarding the card is part of the cost to activate a channel ability.

If a channel ability requires a target, you may not activate it without a target just to discard the card.