FAIRY TAIL Side Stories Vol 1

From the Kodansha edition

DOUBLE DRAGONS Sting Eucliffe, the White Dragon, and Rogue Cheney, the Shadow Dragon. These two powerful Dragon Slayer wizards are the faces of the Sabertooth guild, but they didn't start out that way - both wizards have been down a road of fantastical adventures and hard-won battles to forge their own way as heroes. Learn how two of the most powerful wizards in Fiore got their start!

Source: Anime News Network Encyclopedia