Dice

Critical:

20 classified as an automatic hit/succeed,
If you would naturally hit them with a twenty does Critical Damage/Success
If you would not naturally hit them (20+1 < 23AC) you must roll 2 twenties in a row to do Critical damage
Regardless if you roll three twenties in a row it is an instant kill/success,

Fumbles:

1 classified as an automatic miss/failure
Must succeed on DC 20 Reflex Save or Critically Fumble
Critical Fumbles include:
Injuring yourself/teammate
Damaging items

Dice

Adventures through Trechara IceFrozzen technomageapprentice