Vanguards of the Waves

Reincarnated Individuals are people chosen by the goddess behind the Waves to act as her enforcers in the world(s) that she is fusing. These individuals appear to have been granted a special power by the goddess, such as Tact's ability to steal other people's powers or Ciel's ability to create a perfectly unbreachable barrier. They form an anti-thesis to the Heroes, as they directly work for the force that is trying to destroy the world and work to sabotage or kill the Heroes at whatever time they can. Since they can be recycled after death, Glass' world uses the Soul Eaters to completely destroy their souls after killing them and thus prevents their continued reincarnation.

History
It's been noted that Reincarnated Individuals have appeared throughout history. In Melromark's world they seem to have been used by the Goddess to destroy information that could aid the Heroes in stopping her plans.

The country of Faubley was completely taken over by one reincarnator named Tact, who then attempted to take over the entire world and use his power to steal the Legendary Weapons from their rightful wielders. Tact appeared to be under the impression he was actually saving the world, but because of his sheer selfishness, arrogance and stupidity was in fact leading directly to its impending destruction. He was defeated by the Heroes, Naofumi, Fohl, Trash, Ren ans their comrades, and the weapons he'd stollen found new owners in Raphtalia, Firo, Windia, Wyndia and Midori. He was then promptly executed and his soul consumed by a soul eater. Trash and Naofumi then set about warning the countries of the world to keep an eye out for anyone who matches the description of a reincarnated individual and keep an eye on them to prevent another danger.

In Glass world the situation became much worse due to them not noticing the reincarnator in time. One reincarnator tricked several heroes into distrusting their comrades and killing each other. As many as two are known, one of them being Ciel, who believes the world is a game and that by killing his comrades and instead aiding in the Wave's advance he is letting the game install "Updates". Both reincarnators are noted to be in control of two large kingdoms. Eventually Ciel passes through the Wave and enters Melromark's world, calling it "A new world added by the Goddess' Update," and tries to force the Wave open to get in. He uses his barrier ability to hold off the heroes who desperately attempt to stop him from his goal.

The Reincarnated Individuals seem to be directly in contact with women like Malty Melromarc.

Tact Arusahorun Faubley
A Reincarnated Individual given the power to steal Legendary Weapons by the Goddess. He acts primarily on the belief that he's saving the world, when he's in fact aiding in its destruction. He is Lv.350 and has stollen five of the Vassel Weapons by the time he first appears but ultimately, since he's not actually a hero himself, his power is far inferior to the real Heroes once they get their bearings down and he is promptly defeated and fed to a Soul Eater.

Ciel
A Reincarnated Individual fro Glass world who is under the impression that he's playing a game and by letting the Waves destroy the world and fuse it with Melromark's world he is in fact letting it "Update" and add new lands for him to conquer and new equipment for him to gain. He has the ability to form a perfectly impregnable barrier for a limited time, but he and his allies cannot attack while under its protection.