Hand of Vecna
Legendary Artifact — Equipment
At the beginning of combat on your turn, equipped creature or a creature you control named Vecna gets +X/+X until end of turn, where X is the number of cards in your hand.
Equip—Pay 1 life for each card in your hand.
Equip 
Irina Nordsol
Rulings
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.
(wotc • 2021-07-23)
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.
(wotc • 2021-07-23)
Related Cards
Printings
Rulings
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.
(wotc • 2021-07-23)
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.
(wotc • 2021-07-23)