The content of this page is currently only available in the Japanese version of Puzzle & Dragons. However, it might be added in future updates for the English version.
This dungeon was part of a promo collaboration with 7-Eleven in Japan, and can only be completed once. One of the two 7-11 Dragons will show up. If you don't want the one that appears, you can quit out of the dungeon without killing it and try again, but it will cost 10 Stamina each time.