Taking damage

When a character takes damage, they reduce their current HP by that amount. If they are reduced to 0 HP, then they are out of the action.

When a player character is reduced to 0 HP and the source of the damage was potentially lethal, then the PC is at Death's Door and makes that move accordingly (see Death’s Door). If the source of damage isn't likely to kill anyone, then the PC is simply out of the action: unconscious, gasping for breath, panicking, trapped, etc. Consider asking the player how or why they're taken out. A character disabled this way can't save themselves; they remain disabled until someone helps them, or until you say otherwise.

When an NPC or monster is reduced to 0 HP, their fate is in your hands. If the source of damage was potentially lethal, then they're probably dead or will be soon. Otherwise, they're out of the action and no longer in the fight, but you get to say how. Remember, though: it's not your job to protect your NPCs or monsters. Let things burn.

Followers are NPCs, so you get to decide what happens to them at 0 HP. You can, however, choose to have the player roll Death's Door for them.

If you hurt them, then the lost HP are part of the fictional harm. Otherwise, taking damage means scratches and bruises, sore muscles, rattled teeth, cut lips and bleeding noses, loss of breath, dizziness, pain and weariness and fatigue. It's the wear and tear that grinds someone down but doesn't take them out of a fight.