Vagullion is a boss that appears in Ys I: Ancient Ys Vanished ~ Omen and a mid-boss in Ys Origin. It can split up into innumerable small bats that can swarm its enemies without taking damages to itself. It is only vulnerable during the short time it reforms.
In Ys I: Ancient Ys Vanished ~ Omen, it is a creature found in the mine and annihilated the village of Rastin in a night. In Ys Origin, it is a familiar that Epona summons to challenge Yunica or Hugo. When Epona summons her familiar, she mistakenly summoned two Vagullions, and had to take care of one herself offscreen.
The creature from the mines who annihilated the village of Rastin in a single night. Divides itself into innumerable bats, swarming its prey without mercy. Only vulnerable when it re-forms.
A great, winged demon confronted in the Wailing Blue tier. Capable of splitting itself into innumerable smaller creatures which can band together to inflict severe damage.