Death

When you drop to 0 hit points the following happens and the creature has the condition dying:

   Your concentration is broken.
   Your exhaustion level is increased by one.
   While you are equal to or below 0 hit points, you must at the start of your turn succeed on a exhaustion contest check. The DC equals 10 + 2 for each level of exhaustion and is contested by your Constitution (Brawn). On a failure, you gain a level of exhaustion. This is cumulative.

Whenever you fail an exhaustion contest or when you are reduced to 0 hit points, you may choose to instead:

   Take a fall. The player falls prone this turn and is incapacitated (no action or reaction). The player must be standing to be able to take a fall.

   Fall Unconscious The player falls unconscious for 1d4 hours. Stabilization does not wake the character. An unconscious creature that isn't healed regains 1 hit point when they wake up.

Stabilizing a Creature

A creature who is dying can be stabilized so that it does not have to make any additional exhaustion contest checks each turn. The creature stops being stable, and must start making exhaustion contest checks again, if it takes any damage.

You can use your action to administer first aid to a dying creature and attempt to stabilize it, which requires a successful DC 10 + 1 for each level of exhaustion, Wisdom (Medicine) check. Instant Death

When damage reduces you to equals or exceeds your negative hit point maximum, you die.