C15 Cloud Feather.

The system alert chimed in, "The Moon Feather Heavenly Jellyfish has unleashed its Solo Dancing under Moonlight skill. Players, be on high alert for your safety."

"During the Solo Dancing under Moonlight phase, all players within the arena will see their defenses drop to zero. The attack damage of the Moon Feather Heavenly Jellyfish will surge by 2.5 times