A Homunculus is an artificially created human being. Homunculi were a significant plot point in the Dracul arc of the Sailor Moon musicals, as Death Vulcan convinced his Undead underlings, Death Lamia and Undead Berserk, to create perfect homunculi to replace the human race.
In the first musical of the Dracul arc, Shin / Henshin - Super Senshi e no Michi - Last Dracul Jokyoku, Undead Berserk possessed the body of Professor Souichi Tomoe and took over his lab facilities to further his efforts. He created the Death Mannetjes, but declared them flawed creations as they were made with what he considered to be inferior souls. Count Dracul later joined forces with him with the intention of using the blood of these homunculi to feed his daughter, Bloody Dracul Vampir, as she did not want to drink human blood. Later, Undead Berserk used the Samael Flasks and Sailor Chibi Moon's Star Seed to create suitable homunculi, only to have Count Dracul betray him and steal the Flasks.
In the second musical, Kessen / Transylvania no Mori (Kaiteiban) - Saikyou no Kataki Dark Cain no Nazo, the Samael Quartet were the results of the mixing between the Samael Flasks and Sailor Chibi Moon's Star Seed. Because they were created from her Star Seed, the Quartet felt a connection to Chibiusa.