Artefacto legendario — Equipo
Al comienzo del combate en tu turno, la criatura equipada o una criatura que controlas llamada Vecna obtiene +X/+X hasta el final del turno, donde X es la cantidad de cartas en tu mano.
Equipar—Pagar 1 vida por cada carta en tu mano.
Equipar

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If you control both Vecna and Hand of Vecna equipped to another creature, you choose which creature to apply the bonus to as the triggered ability resolves.
Hand of Vecna's triggered ability uses the number of cards in your hand as it resolves to determine the bonus the creature gets. It won't change if the number of cards in your hand changes later in the turn.