Tanarukk

A Tanarukk as depicted within Volo's Guide to Monsters.

Tanarukks are a species of Planetouched originating from the Forgotten Realms and one of the many "demihuman variants" of pre-existing Planetouched. Specifically, Tanarukks are the Orcish equivalents of Tieflings.

Tanarukks first appeared in 3e as part of the Races of Faerun splat, alongside their fellow "demihuman tieflings", the elf/succubus hybrids called Fey'ri. Their basic backstory is that, 500 years before the present, demons that had been summoned to the material plane conquered a keep in Faerun and took control of it, leading to it being named "Hellgate Keep". From there, they enslaved local orc tribes to serve them, eventually undertaking a breeding program to create a superior strain of fiend-blooded orcs to serve as their slaves. The result were the Tanarukks, a combination of some of the nastiest parts of both races. They had a Level Adjustment of +3, mostly due to starting with 5d8 worth of racial hit dice, and aside from being even stronger and tougher than orcs, were as slow as dwarves but had automatic proficiency with all martial weapons and the ability to cast Control Flame as a Sorcerer of equal character level 1/day.

Tanarukks would later reappear in 5th edition's "Volo's Guide to Monsters". Here, they were portrayed as more generally showing up whenever orcs either turned to demon worshipping themselves or were taken over by a demon-allied black mage; tanarukks, in this edition, are orcs mutated into fiendish versions of themselves in the womb. In this case, however, the Tanarukks' obsession with strength and sheer ferocity means even pureblood orcs are wary of the damn things, and standard procedure is to keep them locked and chained up away from the rest of the tribe when they don't need them. If they get free, their first instinct is to bloodily rampage through the tribe, trying to beat them all into submission so that they can take over. This is bad news for the orcs because Tanarukks are even more warlike and bloodthirsty then their pureblooded kin, usually leading to a conquered tribe being wiped out. As the tanarukk taint can breed true, any tanarukk offspring are usually killed at birth unless the tribe foresees a need for their strength.