User blog comment:Omega natsu2/Chapter 364: Tartarus Arc, Part 1: Immorality and Sinners, Predictions./@comment-112.198.90.65-20131217062144/@comment-7418318-20131217132925

The Vanish Brothers mentioned how they defeated a curse mage, at one point when Lucy looks for a job, there's one for cleansing a cursed item or somesuch and of course there's the "curse" on Galune Island, even though that turns out not to actually be a curse in the end.

When explaining what Lullaby is, they also mentioned curse magic, without ever elaborating what it really is.