In the Planescape campaign setting for the Dungeons & Dragons fantasy role-playing game, the yugoloths are denizens of the neutral evil planes of existence. The Tarterian Depths of Carceri is neutral evil, but is situated "next to" the Abyss, which bleeds some of its chaotic nature across the planes. The Bleak Eternity of Gehenna is nearer to Baator, and thus has some lawful evil attributes. In the middle lies The Gray Wastes of Hades, where it is believed the yugoloths originated.

The yugoloths (which were briefly referred to as "daemons") are a race of insidious fiends whose chief role in the Lower Planes is that of mercenaries. Hiring themselves out to the demons and devils, the bloodthirsty yugoloths play a major role in the politics of the Blood War, for if their race ever entirely sided with either the demons or devils, the war would come to an end. This will likely never happen, if the yugoloths can help it, for they gather vast amounts of wealth and power from the war.

Hierarchy

Lesser Yugoloths

Mezzoloths make up the vast bulk of yugoloth armies and represent the baseline of their race's hierarchy. Mezzoloths form directly from the raw essence of the Gray Waste and Gehenna, either naturally or artificially drawn up from the plane by the engines and spawned pools beneath the Wasting Tower of Khin-Oin and the Tower Arcane (and eventually from the Reflective Chasm in Carceri's Tower of Incarnate Pain). These bipedal, beetle-like fiends wield huge tritons and stand seven feet tall.

Mezzoloths May Be promoted to Dergholoth status.

Above dergholoths, the lobsterlike piscoloths are cruel, hateful bullies who "keep order in the yugoloth armies, a task well suited to their petty and tyrannical demeanor."

Above the piscoloths are the Styx dwelling Hydroloths

Above them are the Yagnoloths, petty rulers given political authority by the Ultroloths

Promoted yagnoloths become Marraenoloths, the boatmen of the river styx, situated upon the cusp of becoming Greater Yugoloths

When a yugoloth angers its superiors, whether through acts of betrayal or desertion, it is punished in a way so terrifying that prospect of such a fate keeps most yugoloths in line. Criminals are transformed into canoloths, the blind war hounds of the yugoloth armies. Forever wracked with pain, the canoloths sense their surroundings by means of a long, thorny tongue. They hate all things and relish the chance to maim and destroy.

There are also skeroloths, formed from demoted mezzoloths, who make up the chaff and fodder for yugoloth armies, acting as spies, thieves, and interlopers. "They serve because they must, fawning over the nearest powerful yugoloth and betraying former masters whenever given a GLIMPSE of richer rewards."

Greater Yugoloths

"Nycaloths are the elite cavalry in yugoloth armies, swooping down onto enemy flanks and tearing up unsuspecting troops." These arrogant, green-skinned creatures are eight feet tall, and possess four muscular arms, a doglike head, and a pair of vast, batlike wings. Nycaloth commanders are bigger and tougher than their fellows, and lead entire battalions into war.

Once a Nycaloth comes to realize the importance of secrets within the greater scope of Evil, and the use and manipulation of these secrets, it may ascend to Arcanaloth status. These jackal or dog-headed fiends dress in fine robes and resemble individual manifestations of a gestalt of the concept of twisted sorcerery. Some of the greatest wielders of arcane magic in the multiverse, they mass within Gehenna's Tower Arcane underneath the leadership of Helekanalaith, the 'Keeper of the Tower', where they record the ProgresS of the Blood War, craft contracts with mortals and fiends alike, and endlessly study the intricacies of abstract evil.

The highest, most pure of the greater yugoloths and the undisputed rulers of the yugoloth race, the ultroloths look like gray skinned humanoids, with enlarged, glowing eyes flickering with malignant color. Their blank FACES are devoid of emotion, and their attitude is one of cold, sterile, distant evil. They constantly backstab and betray one another, and are renowned throughout the multiverse for their unbridled cruelty and malice.

Unique Yugoloths

Although the Ultroloths are the nominal peak of the Yugoloth hierarchy, there exist several other groups of unique 'loths that exist at, above, or separate from this level of power.

The Baernaloths, the original Neutral Evil race of fiends are the puppetmasters and creators of the Yugoloths. Ancient beyond almost all mortal conception, these primordial fiends are the hidden, guiding hand behind the entirety of the yugoloth race, serving as quasi-religious 'advisors' to the most powerful Ultroloths and unique yugoloths whether their words are desired or not. The Baern are the original evils of the Great Wheel, and though most of their kind have since mercifully vanished from the planes or retreated into mad seclusion, their influence, especially that of a group of their kind known as The Demented, is present to those who look for its cancerous traces.

The Oinoloth is both a position and a person, the ruler of the Wasting Tower of Khin-Oin and nominal political authority of the yugoloths of the Gray Waste, though his power is suspect in Gehenna and Carceri. The current Oinoloth is the so-called 'Ultroloth Prince' Mydianchlarus who deposed the former Oinoloth Anthraxus.

The General of Gehenna is the near mythical ruler of the Yugoloth race, something of a racial cult of personality, and said to have been the first Ultroloth, the creator of the first Tanar'ri and Baatezu (or the first Obyriths and Ancient Baatorians, depending on the source).

Altraloths are a group of unique yugoloths who possess unique forms and power above what is normal for their caste, gained through complex bargains with powerful cabals of Night Hags. Despite their power and influence, they are viewed as impure perversions by the rest of their race. Members of this group include Charon the Marraenaloth lord, Bubonix the lord of the Tower of Incarnate Pain, Cholerix, Typhus, Taba, Xenghara and Anthraxus.

There are also the Keepers of the Tower Arcane, the arcanaloth lords Helekanalaith and his predecessor Larsdana Ap Neut, who while hideously powerful and as influential as any Ultroloth, exist partially outside the orthodox hierarchy within their own domains.

Sources

McComb, Colin. 2e 'Faces of Evil: The Fiends' 'Hellbound: The Blood War' 'Planes of Conflict' 'PSMC I' 'PSMC II' 3e Manual of the Planes 3e MM2 3e Fiend Folio 3e MM3 Bonny, Ed. 'Pox of the Planes' Dragon Magazine Annual #2