Blessing of the Potentates is a 3-piece set with Ultimate cost reduction as its main bonus. The 2-piece bonus adds stamina recovery.
This set is mostly used in PVP, but can also sometimes be seen on tanks in PVE. You can obtain a sword, shield and necklace of this set.
The set pieces are named after each alliance. In the pact you have "Pact's Sword", "Pact's Shield" and "Pact's Choker" (necklace). In the Covenant you have "Covenant's Sword", "Covenant's Shield" and "Covenant's Choker" (necklace). And finally in the Dominion you have "Dominion's Sword", "Dominion's Shield" and "Dominion's Choker" (necklace).
Potentates can be an interesting combination with other Ultimate cost reduction sets like Akaviri Dragonguard. You can obtain each set item from the vendor in Vlastarus (Cyrodiil) or get it as a quest reward.