The NWN Online book says,
Saving throws are a measure of a character or creature’s resistance to special types of attacks-poisons, magic, and effects like a dragon’s breath weapon. If a saving throw is made, this may reduce the damage or prevent the effects of the spell or attack entirely.
- Fortitude: This measures your character’s ability to stand up to massive physical punishment, such as poison, paralysis and instant death magic. Your Constitution modifier is added to your Fortitude saving throw.
- Reflex: The higher this is, the better you are at dodging attacks such as a wizard’s fireball or the lethal breath of a dragon. Your Dexterity modifier is added to your Reflex saving throws.
- Will: This save reflects your resistance to mental influence and domination as well as many magical effects. Your Wisdom modifier is added to your Will saving throws.
Saving throws are improved as your character gains levels. Many magic items also improve your saving throws while they are equipped. Several spells can temporarily improving your saving throws, but beware, other spells can lower them!
A Basilisk’s Gaze is saved using fortitude.
Does multi-classing weaken the level based enhancement of saving throws?