Āres (ア - レス - Aresu) is the younger brother of Shion in the Outside Story 2. He was assassinated by Saga, which is then passed to him to be closer to Shion and also down to take the place of Pope. This character does not appear in the manga release.
We know there is a Silver Saint, but we do not know what is its constellation. Because of its status as advisor Pope, it could be the Altar Saint, but no official information is confirmed.