Dominator

Dominator is a greatsword. It is especially effective when fighting daemons.

Source
Dominator can be found as a collectable during Chapter 15 in the Keycatrich Trench maze and near a building northwest of Pullmoor Haven in Duscae (which is southwest of the Alstor Coernix Station); the grey path that falls north of the main road (green) on the map in this area will lead to the building. Dominator can be sold to shops for 6,000 gil.