Through a variety of techniques (e.g. martial training, meditation, ritualistic evocation, mortification of the flesh), some individuals are able to draw upon the energy of their soul to accomplish extraordinary feats. These abilities range from the mundanely superhuman to the explosively magical. Having a strong soul seems to make this easier, but sometimes even people with fragmented souls are able to accomplish the extraordinary. The individual's body seems to act as a conduit and battery for this power, drawing in replenishment from seemingly omnipresent "fields" of unbound spiritual energy in the world around them.
So souls are the main source of power in this game. It's pretty different, which is good. It's not just make sign=magic spell.
The cultures of Project Eternity are in a variety of different technological states. Though some remote civilizations are still in the equivalent of Earth's Stone Age or Bronze Age, most large civilizations are in the equivalent of Earth's high or late Middle Ages. The most aggressive and powerful civilizations are in the early stages of what would be our early modern period, technologically, even if they are not culturally undergoing "Renaissance"-style changes.
It's not purely medieval like normal fantasy either. It's everything from the stone age to the late Renaissance in technological terms, leaving quite a stretch of potential enemies. And that means guns.
Black powder firearms are of the single-shot wheellock variety. Largely considered complex curiosities, these weapons are not employed extensively by military forces. Their long reload times are considered a liability in battles against foes that are too monstrous to drop with a single volley, foes that fly or move at high speed, and foes that have the power of invisibility. Despite this, some individuals do employ firearms for one specific purpose: close range penetration of the arcane veil, a standard magical defense employed by wizards. The arcane veil is powerful, but it does not react well to the high-velocity projectiles generated by arquebuses and handguns. As a result, more wizards who previously relied on the veil and similar abjurations have turned to traditional armor for additional defense.
Guns are mostly used for counter-magic, which is an awesome idea I think.