If Squall isn't on the battlefield as its last ability resolves, use its power as it last existed on the battlefield to determine how much damage the ability deals.

Squall's last ability checks the power and toughness of the attacking creatures at the moment it would trigger. If none of them have power or toughness equal to the chosen number, the ability won't trigger at all. If it does trigger, the ability will check the power and toughness of those creatures as it tries to resolve. If none of them have power or toughness equal to the chosen number, the ability won't resolve and none of its effects will happen. If any of those creatures have left the battlefield since the first time the ability checked their power and toughness, use their power and toughness as they last existed on the battlefield.