Seraph Crystal Are a new type of currency introduced to the game by the first campaign DLC Captain Scarlett and Her Pirate's Booty. The Seraph crystals drop from the two new "Invincible" bosses known as "Seraph Guardians". Master Gee The Invincible and Hyperious The Invincible become available in missions from Shade after completing the main story missions of the DLC. The first missions you will receive is "Hyperious the Invincible". After defeating Hyperious the mission "Master Gee the Invincible" will become available.
Seraph crystals can be used in exchange for new weapons in the town of oasis. The new weapons sport a pink name text and are know as "Seraph" rarity, which places between the rarity of very rare (purple) and legendary (orange). The weapons/shields all cost 120 seraph crystals with the exception of the Blood Of Seraphim Relic which costs only 50. All of the weapons/sheilds, including the Blood of Seraphim relic, sport a red flavor text.