Alright guys, so me and my friends just completed the entire DLC (Story & Side Missions). Now I have to say, he must be the hardest MFer to beat. Just because you cannot deal direct damage to him. Anyways, after we beat him, we went to go at it again and we got this message: "One or more players in your party have beaten this boss today." Something like that, so that means we CANNOT farm this boss AT ALL unless someone finds a way around it. From what I know so far, Seraph Crystals are dropped by the two raid bosses. Hyperius & Master Gee the Invincible. They dropped a total of 7 each. Each gun in the Seraph Crystal Black market costs 120 Crystals.... I hope some of this info helps you guys. Happy hunting (& once a day farming).