Vantress Gargoyle

Flying
This creature can't attack unless defending player has seven or more cards in their graveyard.
This creature can't block unless you have four or more cards in hand.
{T}: Each player mills a card.

Throne of Eldraine Promos

Throne of Eldraine

If Vantress Gargoyle attacks a planeswalker, the controller of that planeswalker is the defending player.

Vantress Gargoyle's attacking and blocking restrictions are checked only at the moment that you declare it as an attacking or blocking creature. If the defending player loses cards from their graveyard after Vantress Gargoyle attacks, or if you lose cards from your hand after it blocks, it remains in combat.