Curoller is fought along Cernunos, he can summon two of those during the battle, and keep reviving then, until you kill him. Although it can't attack, those little pests can cast Defend, to increase the whole enemy party's defense, and Cure, to heal Cernunos for a significant amount of HP. While they can be annoying, killing both isn't recommended, as Cernunos starts using its one-hit kill attack if it happens. Always leave one of those alive, although the constant healing is annoying, getting a dead character is much worse. Also, as long as one is alive, the second Curoller will not revive.