The child of Medusa Gorgon, Crona is a Demon Sword Master whose weapon, Ragnarok, resides permanently in his/her body. He/she is androgynous in appearance, and is presented with an ambiguous gender throughout the series. Although there have been hints towards Crona’s gender in both directions, nothing definitive has been presented.
Beautiful cosplay! Although I’m not sure whose weapon is in the foreground of this photo since I’m not familiar with the series. Could it be Maka’s scythe? Thanks to Aerie for suggesting this!