Death Saves

Death saves are the player's last chance to save themselves.
Upon 3 failed death saves, players will not immediately die. They will be unable to make any action and will suffer 2 levels of exhaustion per turn.
Think of it like receiving a mortal wound and bleeding out -- not instantaneous, but slowly weakening the player as they die.
If the player is saved by a party member, they retain all levels of exhaustion and will remain unconscious until a long rest is taken by the party.
If the player is not saved, they will die when they reach the 10th level of exhaustion.