Also known as daemons (no, not those Daemons), Yugoloths are the neutral evil equivalent of the devils and demons in Dungeons & Dragons. Just like the Baatezu and Tanar'ri, they had their name changed to its current form in 2e, because the ancient Greek word for “spirit” is FAR too satanic to put in an RPG. Yugoloths aren't nearly as popular as the two other major fiendish races, nor are they as well known. Yugoloths are originally from the Gray Waste of Hades, though nowadays most of them live in Gehenna.
Yugoloths embody the platonic idea of Evil itself. Not “evil”, mind you, but captial-e Evil. They lie, cheat, and betray for its own sake, and generally seek to cause as much suffering and hate as possible to everyone. They're kind of dicks like that. They act as mercenaries in the Blood War, constantly switching sides between the Baatezu and the Tanar'ri (this can happen multiple time in a single battle). In fact, there's conspiracy theories that they are the original fiends and/or that they're the ones who started the Blood War and are playing it to their own end.
Because of this, Yugoloths haven't fared too well in the post AD&D editions. With Planescape not getting an official 3.x release, and the Blood War thusly getting a lot less shilling, they were mostly forgotten aside from the occational update in a Monster Manual. In 4e they lost their whole reason to exist with the almost non-existant Blood War and were instead made a subtype of Demon. The jackal-like Arcanoloths were even divorced entirely from the Daemon family tree and made an entirely new species of scheming, manipulative evil immortals called Ravasta.
In 5e, Yugoloths were created by the Baatezu in order to combat the Tanar'ri. However, the Baatezu lost control of them, and now they're a mercenary fiend race giving their help wherever the most profit is to be made.
The Truest Fiends
The Yugoloth maintain a number of strongholds on the Lower Planes. Their biggest one is the Crawling City making its way on the slopes of Gehenna. Here the General of Gehenna, the leader of the Yugoloth, holds his court and plots against the Multiverse itself. Also on Gehenna is the Tower Arcane, where the Arcanoloth record all the deals made with mortals and Outsiders alike. Hades houses Khin-Oin, a massive tower allegendly made from the spine of a deity the Yugoloth killed. Here many of the soldiers of the Yugoloth armies live and train. Finally there is the Tower of Incarnate Pain, which is still under construction in Carceri. Made from the screaming bodies of petitioners and the skin of a dead god, the Yugoloth intend to use the tower to link their two other towers and obtain considerable power that way. The native inhabitants of Carceri, the Gehreleth do not agree with this and frequently attack the tower to tear it down. Without their attacks the Yugoloth would have been done centuries ago, but because of the actions of the Gehreleth they are far behind on schedule. While the fiends are very limited in number and the Yugoloth could easily crush them with a superior force, they do not do this because it would draw too much attention to their secret project.
The Shapes of Evil
- Guardian Yugoloths: Least, Lesser, Greater.
- Battleloths: Arrow, Axe, Crosbow, Pick, Spiked Chain, Sword.
- Arcanaloth: Probably the most famous of the Yugoloth species, Arcanloths look like anthropomorphic jackals and are known for managing the mercenary contracts that are the lifeblood of the Yugolothic personal involvement in the blood war. In essence, all contracts to hire Yugoloths ultimately get approved by these guys. These guys are perhaps best known because they have two representative characters living in Sigil; A'kin the Friendly Fiend, a seemingly benevolent (not that anyone buys it) merchant, and Shemeshka the Marauder, aspiring to be the biggest wheeler-dealer in the Cage, who calls herself "King of the Crosstrade" and is famous as one of the first canonical genderconfused NPCs -- she calls herself female, but her profile in the Sigil bigwig NPC splat "Uncaged: Faces of Sigil" depicts her with a male symbol, implying she's trans. Of course, according to Faces of Evil, all Yugoloths are hermaphrodites, so that means she's actually a dickgirl.
If they are willing to serve the Night Hags for a specific purpose, a Yugoloth can choose to undergo a ritual to become a powerful new being: an Altraloth. In a long and painful ritual any Yugoloth from Mezzoloth to Ultraloth can be turned into a new creature of superior power, but to do this they will have to enter a contract with the Night Hags and complete its terms before being freed. Most Yugoloth chafe at this because they are not able to betray their new mistresses: hurting them will result in unspeakable pain for the Altraloth, and if one of them were to die for any reason the Altraloth perishes as well. As such, they are invested to the wellbeing of their masters and will do anything to protect them.
Apomps the Three-Sided
Anthraxus the Decayed
The General of Gehenna