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Trample
Whenever Mindleech Mass deals combat damage to a player, you may look at that player's hand. If you do, you may cast a spell from among those cards without paying its mana cost.
The card is cast from your opponent’s hand, not yours.
The spell is cast during the resolution of Mindleech Mass’s triggered ability. You may cast any nonland card in the player’s hand, not just an instant card. This doesn’t get around other prohibitions, such as “Cast this card only before attackers are declared.”
You choose modes, pay additional costs, choose targets, etc. for the spell as normal when casting it. Any X in the mana cost will be 0. Alternative costs can’t be paid.
You control the spell and, if it’s an artifact, creature, or enchantment spell, you control the resulting permanent.
