Massive Damage

If you take damage from a single attack that reduces you to 0 HP and there is damage remaining, you die instantly if the remaining damage is equal to or greater than your maximum Hit Points. If you take damage from a single attack equal to or greater than your maximum Hit Points while you have 0 current HP, you die.

Suppose Navasi has a maximum of 22 HP, but she currently has 5 HP and 0 SP. She takes 30 damage from an enemy. Navasi is reduced to 0 HP, with 25 damage remaining. Since this damage is greater than her maximum Hit Points, Navasi dies.