Akiba Guild Hall Raid

The Akiba Guild Hall Raid (アキバギルド会館レイド) is an event that occurs in the thirteenth volume of the Log Horizon series.

Overview
Lelia Mofur and Litka Mofur warn Log Horizon about a Genius, Eirenus, who has prepared to attack Akihabara. This premonition comes true when Isaac and his men wake up in an area where they hadn't been when they fell asleep. Knowing that this is the work of Genius, having been warned by Shiroe beforehand, they uncover the level 65 Eirenus and attack him, but are easily defeated and killed.

Meanwhile, Akihabara has not only been turned into a Raid zone, but Eirenus has employing some sort of Mentor System-like Overskill, suppressing anyone whose level was above 65 all the way down to level 35. Furthermore, zone connections have been screwed up and thus zones don't connect the way that they normally would (for example, the door to the kitchen of the guild hall could now connect to the outside of the Akiba Baths). To worsen the situation even further, it is impossible to contact others with Telepathy, making organizing much more difficult.

Realizing that he and the other formerly-high-level players don't stand a chance against the level 65 enemies, Shiroe has Lelia and Litka (who are at level 65 and thus didn't have their levels lowered) find Minori and have her organize a counterattack. Minori, upon receiving the message, finds members from the Crescent Moon Alliance and Log Horizon to form the Akiba Guild Hall Raid Party.