Lot of times characters will face critical situations and they will have to see if their chance to resist to something or to notice something is successful or not. For these occasions the GM will roll one of the following against a DC (like other skills):

SAVE / CHECKCODEDESCRIPTIONCALCULATION
Fortitude SaveFORT chance to resist effects targeting the body’s toughness (e.g. poison)1d20 + LVL + STR modifier
Reflex SaveREFChance to resist effects targeting the body’s reflexes (e.g. avoiding an arrow)1d20 + LVL + DEX modifier
Willpower SaveWILLChance to resist effects targeting the mind (e.g. resist charm) 1d20 + LVL + WIS modifier
Perception CheckPERChance to notice something or being aware of something 1d20 + LVL + INT modifier