Youma are the monsters of the day in the first arc of the Sailor Moon anime and in the live-action series. All of the Shitennou, as well as Queen Beryl and occasionally Metalia herself, use youma to achieve their goals. Although the origin of earlier Youma is not shown, Kunzite's Youma are created from human beings in the anime. Any Youma created from humans can be returned to their human form by Sailor Moon using Moon Healing Escalation (which restores the human while destroying/expelling the Youma side) while others would be finished off by Moon Tiara Action (or other Senshi's attacks on occasion; see below). In the English anime members of the Negaverse refer to the Youma as their "servants", while the Sailor Scouts and Tuxedo Mask just call them "monsters" or sometimes "Negamonsters".
Read more about this topic: Queen Metallia