An anthropomorphic gender-swapped lolified Cthulhu wearing a gym uniform in a Strike Witches parody... No emoticons conceived by the minds of mortal men could properly convey my thoughts right now
The two girls on the left side are Elder things, the upper left side one is holding a Shoggoth, the girl on the right is Cthulhu.
This image is likely a reference to "At the Mountains of Madness, where it is told that the Elder things shortly after arriving on this world, waged war with Cthulhu and his spawn. They also created the Shoggoths to be their slave race, they also created all life on this planet including mankind. Eventually the Shoggoths rebelled and destroyed their creators.
There, that should adequately explain it, 12 months after its posted.