A player who controls a creature that “attacks if able” can decline to pay additional costs to have that creature attack. If they do and there’s no other player or planeswalker to attack, that creature simply doesn’t attack.
2022-09-09
In a Two-Headed Giant game, creatures can attack your teammate and planeswalkers your teammate controls without requiring a life payment.
+1: Until your next turn, creatures can't attack you or planeswalkers you control unless their controller pays 2 life for each of those creatures.
−3: Search your library for a Dragon card, reveal it, put it into your hand, then shuffle.
