Rule 702.46a

Splice is a static ability that functions while a card is in your hand. “Splice onto [subtype] [cost]” means “You may reveal this card from your hand as you cast a [subtype] spell. If you do, copy this card’s text box onto that spell and pay [cost] as an additional cost to cast that spell.” Paying a card’s splice cost follows the rules for paying additional costs in rules 601.2b and 601.2f–h. Example: Since the card with splice remains in the player’s hand, it can later be cast normally or spliced onto another spell. It can even be discarded to pay a “discard a card” cost of the spell it’s spliced onto.

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