On 12 May 2012, the one-week Avenger Event was officially announced. 
From 12th to ? of May, you were given a chance to get the 9 Avengers Treats and a special trophy.
This trophy can only be obtained during the event.
In order to gain the trophy, you had to defeat the minipet LOKI and gained the Tesseract.
>> LOKI (Trickster Treat)
With the Tesseract, you will be able to redeem in it for the trophy.