"Fairy Tail" Chapter 509 spoilers revealed Mavis as the mother of Larcade. And since Kagura is not able to defeat Larcade, Mavis will not have any choice but to fight Larcade, presumably her own son. This she has to do or Larcade will kill the "Fairy Tail" members.

Larcade's Magic Is Both Pleasurable And Toxic

The helpless members of the guild in "'Fairy Tail" Chapter 509 are in a quandary. They feel the pleasure of Larcade's magic, but at the same time also realizes the agony that he has brought upon them. Larcade uses this "Pleasure" strategy to anyone who already tasted "the forbidden taste of pleasure."

Kagura Is Coming To The Rescue

When some of the members of the Fairy Tail gang appear to be dying, Kagura appears to join the fight against Larcade. As a pure mermaid, she has not tasted pleasure before and therefore was not affected by Larcade's magic powers. She told Larcade that she can't understand why he became a comrade of the Black Wizard. But Larcade said: "I am much more than his comrade....Zeref is my father."

Spoilers For Chapters 509 Of "Fairy Tail"

Some are speculating that the upcoming chapter will reveal the real identity of Larcade - as the son of Mavis and Zeref. This was probably made possible because of the curse that Zeref possesses. When he kissed Mavis, they were both under the curse which made her pregnant with a son, who later turned out to be Larcade.

This would really create an interesting twist to the fight that might occur when Mavis and Larcade face each other. However, some also suggest that Larcade might not be a biological son of Zeref. He could probably be just a creation of his. Perhaps the future chapters will reveal the real origin of Larcade.