Supernatural creatures are rare entities, powerful and nearing demi-gods with the extent of their power. Their powers grant them extraordinary defense and offense which mortals pale in comparison to.
As threats, supernatural entities are meant to be late game/high level enemies only to be fought if and when the group is prepared for such an encounter. Especially in games where the party is filled with humans, the presence of supernatural beings can leave them speechless in fear and awe.
Few Supernatural Beings vs. Many Supernatural Beings
Depending on your campaign, you may want to make creatures of the supernatural type more common (and thus, encountering unnatural creatures includes much more risk. If you want this kind of game; Aberrant, Dragon, Fæ, and Outsiders are all supernatural by default while other creature types still require it to be listed in their individual creature entry.
Player Species aren't supernatural by nature, even Outsiders like the Angel and Demon, though present as options, aren't supernatural variants of their kind. When playing with this rule, it's recommended you keep this the same if you don't outright ban these kinds of species from play.
Supernatural Weapons multiply damage by 10 against non-supernatural creatures.
Supernatural Armor takes no damage from non-supernatural weapons.
Supernatural Creatures are impervious to non-supernatural weapons, and their unarmed/natural attacks are Supernatural Weapons.
Deities and deific-powered entities are supernatural in nature but also possess divinity, making them even more dangerous. Divines are impervious to non-supernatural weapons, and supernatural weapons are able to deal damage to deific entities but not kill them.
There will be further rules for divine and supernatural entities in later entries.