Coin of Teva is a quest item. When the quest is released, you visit the NPC (Guard Shutian if I remember right) and follow his instructions. If done right, you will receive a permanent mini-pet called "Coat of Arms". It's a limited item, each server has a different color. The mini-pet rotates/glows last time I remember. (I designed the item, go me!)
There is a back story I created behind this item. It will lead up to a larger story that leads into some new content on the way and ultimately end game content in development. I can't divulge what that will be but there are some clues to my initial paragraph.
This is one of our efforts in trying to make Fiesta "fun" again. Notice no premium items needed for these events
And it's limited edition permanent item.