Fiendlings are mortal creatures who have had their usual ancestry mutated by some influence of the lower planes. They are one of three types of planetouched. Fiendlings may be the result of an ancient blood debt to a devil, a demonic possession, or even just the whims of influential evil gods. Although they can be born to any other ancestry, humans are the most easily corrupted by fiendish influence, making fiendlings most common in human societies.

Fiendlings are created by planar interference and may be born to any other ancestry, usually bearing no similarities to their parents. They stand between five and six feet tall and have builds similar to humans. Fiendling eyes are a single solid colour with no pupil and may be black, silver, or gold. Regardless of their parentage, fiendlings mature in 15-20 years and live up to 100 years before the planar influences that created them fade, killing them. This process is sudden and without warning, and a fiendling will show no signs of their old age.

Depending on the nature of the fiend that caused their creation, other aspects of a fiendling's physical appearance will vary. Fiendlings created by devilish influence will have red, pink, or light tan skin and may have horns and thin tails whereas those created by demonic influence will have grey, dark grey, or blue-tinted skin and may have clawed hands and hooves for feet. A combination of these features may exist when even higher-power fiends are involved, especially the gods of the lower planes.

Fiendlings may be intentionally or unintentionally created by the gods and godkin of the lower planes. For example, a devil may intentionally make a deal with a mortal creature which causes their offspring to be fiendlings. Or, a cult performing a demonic ritual may cause the birth of a fiendling in the a nearby village. Even though they are not inherently evil, fiendlings are frequently ostracized by their communities and sometimes even their own families.

Because they are born to other ancestries all over the world, fiendlings' names and known languages depend on where they were born and raised. Early in life, many fiendlings will hear the whispered words of evil entities from the lower planes trying to corrupt them and may learn their languages that way.

As gods and godkin learnt the power of mortal worship, they began exerting their influence over Aedelor in various ways. The boundary between the outer planes and Aedelor was thin enough to allow them to perceive the world, but still too strong for them to traverse the planes. As the mortals in Aedelor became more aware of the other planes and developed mastery over magic, they too became interested in the outer planes. A crafty devil from the lower planes discovered a way to communicate across the planes and made deals with various people who were too easily corrupted by the promise of power.

The evil and destructive power of the lower planes began to bleed through into Aedelor and tainted the lineage of the people making these deals. Though the boundary between planes was still too strong to traverse, devils planted the seeds for what would become lower planetouched generations later, as the price of the pacts began to come due. Powerful creatures from the lower planes continue to exert their will over Aedelor in places where the boundary is weakest, or by making deals.