DelveDelve is a static ability that functions while the spell with delve is on the stack. “Delve” means “For each generic mana in this spell’s total cost, you may exile a card from your graveyard rather than pay that mana.”
The delve ability isn’t an additional or alternative cost and applies only after the total cost of the spell with delve is determined.
Multiple instances of delve on the same spell are redundant. (CR 702.66) (Each card you
exileTo exile an object, move it to the exile zone from wherever it is. See rule 406, “Exile.” (CR 701.13) from your graveyard while casting this spell pays for
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MillFor a player to mill a number of cards, that player puts that many cards from the top of their library into their graveyard.
A player can’t mill a number of cards greater than the number of cards in their library. If given the choice to do so, they can’t choose to take that action. If instructed to do so, they mill as many as possible. Similarly, the player can’t pay a cost that includes milling a number of cards greater than the number of cards in their library.
An effect that refers to a milled card can find that card in the zone it moved to from the library, as long as that zone is a public zone.
Some spells and abilities mill a single card and then ask for information about the milled card. If more than one card is milled due to replacement effects and the effect of a spell or ability asks for information about the milled card, such as a characteristic or mana value, it gets information from each milled card and will get multiple answers. If these answers are used to determine the value of a variable, the sum of the answers is used. If that effect grants a player permission to cast or play “that” card, the permission applies to each of the milled cards. If that effect performs any actions on “the” card, it performs that action on each milled card. If that effect performs any actions on “a” card, the controller of the spell or ability chooses which card is affected. (CR 701.17) two cards, then return a nonland card of an opponent's choice from your graveyard to your hand.