Magic

Two realms enshroud the physical world - the Aether and the Void. The Aether is a replenishing membrane whence magic stems from, and reshaping reality with magic depletes the Aether. The Void is a mystical realm where the eponymous Void God resides and Voidspawn originate. Where the Aether is thin, Voidspawn may slip through and occupy a living host, wherafter they gradually overtake their mind and body.

The origins of the Void and Aether lie in the Maker, where the latter is his symbolical life blood. As the Aether's origins are thus divine, its world-altering potential is unknowably vast, perhaps unlimited. However, no one but perhaps the Starshapers has plumbed the depths of this power, and their defeat and vanishing are a testament to even their limits.

In order to tap into the Aether, an individual must bear the mark. Void storms barrage the Aether relentlessly, and their lightning may momentarily pierce even barely grazed portions of it. As these strikes of lightning cannot bear a Voidspawn whole but only their seed, birthed and formed souls are impervious. Only a nascent soul still bound to its begetter, such as a yet not born child's in their mother's womb, may become marked by the Void.

The mark of the Void manifests as a sort of birthmark and its position and shape are largely random, as they depend on where and how the Void lashed at the soul. Wizards have attempted to gain insight into the Void via studying this. The skin is darker, number, and far toughter. A dagger is unlikely to pierce, only the hottest flames will singe, and magic cannot affect the mark.

Despite the mark's peculiarity and both commoners' and scholars' obsession with it, it is not the source of the skill to tap into the Aether, but merely a physical manifestation of what is underneath - an altered soul. In a twisted way, marked ones differ little from Voidspawn themselves, which is why Voidspawn, when plummeting through the Aether, cannot and do not attempt to corrupt them, for they instinctively do not target their own. Just as Void storms rake the Aether, so do mages take from it, and so do marked ones attract Voidspawn as flames do moths, who believe they are seeing their Voidkin already bound to mortal hosts.