Pledge of Friendship: Thunder Bluff

A Pledge of Friendship: Thunder Bluff is a container item obtained from (guard) NPCs in Thunder Bluff during the Love is in the Air seasonal event.

Source
You get Pledges of Friendship: Thunder Bluff from Bluffwatcher NPCs in Thunder Bluff in exchange for.

Contains
Opening a Pledge of Friendship: Thunder Bluff by right clicking it creates either a or a  pledge gift. The odds of getting either pledge item appear to be about even, but in the short run you are likely to get a stack of one while trying for the other. You must have room in your inventory, an open slot in your inventory or a stack of less than 20 of the item you get, in order to create the item.