Armor Class
- Magical AC bonuses from shields and armor do not stack
Critical Hits https://www.dndbeyond.com/sources/phb/combat#CriticalHits
-
"When you score a critical hit, take the maximum damage of the attack's
damage and in addition add the dice roll for the attack's damage
against the target. Then add any relevant modifiers as normal. To speed
up play, you can roll all the damage dice at once."
- Only applies to player characters (not monsters or NPCs)
Dropping to 0 Hit Points
- Characters who are dropped to 0 hit points and go unconscious increase their Stress Score by 1
-
Characters must succeed on a saving throw (modified by their Stress) or
suffer one level of Exhaustion if they have any Stress at the end of
combat
- Stress Score is set to 0 afterwards