Bloody Valkyrie Incident

The Bloody Valkyrie Incident was a battle between Ainz Ooal Gown and a brainwashed Shalltear Bloodfallen.

Background
During a mission undertaken by Shalltear Bloodfallen, the Floor Guardian caused a disturbance, annihilating an iron ranked adventurer team. One of the adventurers managed to slip away and escape back to E-Rantel. The Guildmaster Pluton Ainzach learned from the survivor that the team had faced a powerful vampire with abnormal abilities. Usually, a platinum ranked adventurer would suffice to eliminate the monster, but given the circumstances, Pluton decided the best course of action would be to summon all mithril ranked adventurers and handle the situation from there.

Incident
Ainz Ooal Gown upon learning that a Shalltear had rebelled against Nazarick, quickly teleported back to the Great Tomb of Nazarick. They're using the dungeon's administration system, he determined that Shalltear was under the control of outside influence. Later he and Albedo go to the 5th Floor to visit Nigredo and use her to find Shalltear. They discover that Shalltear is now fully equipped in her Bloody Valkyrie form. Ainz then learns that the Adventurer's Guild in E-Rantel is looking for him. Resuming his identity as Momon, and goes to the Adventurer's Guild meeting. The meeting had summoned several other mithril adventurer teams: Darkness, Rainbow, Sky Wolf, and Kralgra. The plan was to have the adventurers combine their forces to defeat the vampire. Knowing this would be detrimental should his connection with Shalltear be discovered, Momon interjects stating that they would all die.

Momon insists to the Guild leaders, E-Rantel's authorities and his fellow Mythril adventurers that he will exterminate the vampire. He concocts a story that tells him he is familiar with the vampire, as he has been hunting her, Honyopenyoko, and another vampire. All of the people in the room are aware of Momon's reputation but are doubt that he alone could defeat the vampire alone.