Just after a couple of hours of searching, Uriel found the possible central location of the ritual.
Notice: One of the Dark Shadows found a concentration of Mana just a few miles away from here. The immense Mana seemed unnatural and looks to come from multiple Holy Relics instead of the shards of the broken staff of wisdom.
"Gather all my dark shadows back. If they are too far away, let them meet with a dark shadow nearby and kill themselves or fight a random monster they find along the way."
Notice: Prioritizing calling in only the close Dark Shadows and killing Dark Shadows too far away from the user.
(It's quicker if I just resummon them here than wait for them to travel for miles since they don't have teleportation skills. Hmmm... Since the Demon Monarch specializes in summoning magic, I hope that if I somehow complete the Dark Monarch set, I get to learn a skill on teleportation for my summoned units.)
