Siren's Song—this was the active effect attached to the Song of the Siren trinket that Izroth obtained after he defeated the Head Master of Siren, Smiling Demon.
It greatly enhanced the perception of Izroth and his allies while simultaneously lowering that of his enemies. This made it ideal for group fights and small skirmishes. More importantly, it was an item capable of changing the flow of battle.
Not long after Siren's Song took effect, the members of the 9th Division and 5th Unit finally started to push back and gain some ground against the shadahi.
With the enhancement to their perception, those who were a part of the vanguard were able to react in a much more timely manner when it came to intercepting the Demonic Charge skill of the shadahis.
Furthermore, the execution and timing of the heals or protective-type skills being cast by the supporters improved greatly.