As explained in Chaos Rings Omega, Congloms are biological creations made from the genetic material of different organisms, hence the name Conglom, possibly derived from the word "conglomeration." All enemies in the dungeons in the Chaos Rings series are Congloms, as well as Yorath. Their purpose, as deemed by Theia during the founding of the Ark Arena, is to strengthen the participants of the tournament in hopes of creating stronger descendants later. As revealed in the prequel, Cyllis herself gives birth to all Congloms and considers all of them her own children. they are spawned in the Conglom Plant, a negative version of Bereshith Road.
It's unknown where the Congloms come from in Chaos Rings, as Cyllis was apparently destroyed completely in Omega.