Power Crystals

Called many names by cultures around the world, 'power crystals' are rather unassuming and often ineffective without magical treatments, but these gems are able to draw power from the Girdle of the Gods, serving as a conduit for magical energies and allowing magical technology to function. Very similar to Marks, power crystals can be made from the Marks of the deceased, though this is seen as a poor use of the valuable Mark crystals which often carry memories in addition to their powers. On rare occasions a Mark is deemed suitable for a sword or similarly unique and important artifact, but slapping one in a rifle is considered extremely distasteful.
Most power crystals are dug from the ground, and can take many forms; really and crystal with a degree of conductivity is suitable. Wizards know rites and rituals to infuse these crystals with conductive ability, and the Girdle of the Gods is a seemingly endless source of energy (it is, after all, the power with which the gods shaped Kytheria to begin with). The enchantments on crystals can fade however, and few last longer than a few years without renewed rites performed on them. Marks and other crystals which naturally conduct Girdle energy can last for centuries, but the latter are extremely rare. Not having to pay wizards for charging their power sources makes natural conduits extremely valuable, as most wizards belong to guilds and understand the monopoly they possess. Black market Marks are also a possibility, though the superstitions about the ghosts of prior owners are very much founded on a dollop of truth.
The issues with these crystals include not only susceptibility to location (the further one gets from the equator, the less energy is generally conducted), but there are also a lot of people who believe that excessive crystal use can disrupt prana in a local area, shredding or wounding the natural magics of the world. Several societies shun magical technology for this reason, and seem to get by adequately without it. 'Civilization' has come to have a connotation of power crystal use with more rural or 'backwards' people eschew them, though there are many cases where a small handful of crystals are seen as valuable for the warriors of a town, but aren't used willy-nilly in city infrastructure or anything similar.