Takenuma, Abandoned Mire

{T}: Add {B}.
Channel — {3}{B}, Discard this card: Mill three cards, then return a creature or planeswalker card from your graveyard to your hand. This ability costs {1} less to activate for each legendary creature you control.

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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.

The creature or planeswalker card you return to your hand is not chosen until after you mill three cards. You may choose a creature or planeswalker card from among all the cards in your graveyard, including the milled cards.