What do u think is the Most Mysterious thing in Fairy Tail Anime............!!!!!!!!!!!! (For Fairy Tail anime Fans)

it can be a character...or a magic.......or an Artifact.......!!!!!!!!

As for me whats really mysterious for is

The Lumen Histoire

i really am curious to see what will happen when its released......
Mavis is a friendly Mage but still why is she feared bởi all........and other Guilds Searching for it.....!!!!!!!!!!

ok thats for me........
now here is the Challenge there r other tons of Mysterious things in Fairy Tail which is not revealed yet
so what is ur Mysterios thing from this anime

Best Answer will receive 10 props.............!!!!!!!!!

So whats urs...........????