Buffy Summers and the Scooby Gang faced a powerful soul-eater known as the Triumvirate, the Three-in-One, which could take the soul of those who touched it, leaving the bodies alive but mindless for its vampire minions to feed on. The Scoobies defeated it with the aid of the spirit of Slayer, Lucy Hanover, the guardian of the ghost ways, who arranged for their bodies, with the obvious exception of the already-dead Angel, to be temporarily "killed" and possessed by the dead, thus preventing the Triumvirate from feeding on their souls and allowing them to defeat it by starving it after it had been brought into this world.
Angel Investigations faced Shug, the last of a race of soul-eaters known as the Kurgarru, who survived the extinction of his kind after all other ensoulled life in his dimension had died out by feeding on his own wife and children before being drawn into this world. Shug and his human minions were responsible for an elaborate black market trade in souls being carried out, with the soul of an innocent child being a particularly valuable commodity, but Shug was killed when he and his partner turned on each other due to their disagreement over whether they should sell Angel's soul or allow Shug to eat it.
A more primitive type of soul-eater was buried by the Chumash people in the early 19th century. Charles Gunn and Connor sought the skull of the soul eater after being sent to retrieve one by Cordelia Chase, who was secretly possessed by Jasmine.
Jamaerah had grown Liss, a female Soul Eater (of a different species to the one Gunn and Connor had encountered years earlier), from the body of a murdered tenant and enlisted her as his agent against Angel and Spike. Liss used a client of Angel Investigations to gain direct access to the Hyperion hotel in order to consume the souls of both vampires, but a spiritual parasite that had infected Spike prevented her from sensing his soul, allowing them to poison her with an elaborate potion using Illyria's blood, although she was still able to stay alive long enough to kill their teammate Dez.
The first Soul Eater encountered by Angel Investigations had the ability to drain the soul and lifeforce of humans through its hands. It was also capable of moving at extreme speeds, making it nearly invisible to the human eye. It was also capable of surviving decapitation and could live without oxygen for centuries.
While Liss also shared the power to consume souls through touching, her additional abilities included superhuman strength, the ability to control the body of those she drained for a 24 hour period, and the ability to detect the presence of souls. Liss could physically pass as a human and was able to function as such although she had an impatient and blunt demeanor.