Akrida

The Akrida are an extradimensional species from another universe.

Biology
The Akrida are an insectile species with three pairs of jointed legs and a pair of shorter limbs that resemble pincers. Their eyes are greyish eyes and possess numerous needle-like teeth. Similar to insects, they possess a social caste system, having a queen as their leader. They are parasites and are able to control and possess humans with their stingers.

The Akrida were said to be immortal and nothing in the current universe that they invaded could harm them. However there was a loophole in that other beings or objects from other universes, aside from the one they were currently in could do them harm.

History
The Akrida were one of the last creations of God, created as a failsafe to destroy all life in every universe should he fail or lose.

For untold ages the Akrida were left with the knowledge that they were simply creations of an "angry god", however during the 17th century of particular universe, their world was visited by a human immortal named Joan Hopkins who had come to a belief that humanity was the problem and sought to eliminate them from Earth. For her transgressions, she was banished to their world by the hunters and Men of Letters as she was an existence that could not be killed.

Joan quickly became their queen who the Akrida adored as she gave them a new purpose. Sharing her nihilistic beliefs, they changed their goal from destroying the multiverse, to ending the tyranny of mankind across all realities. Over the centuries, Joan would lead her followers to attack her reality, aiming to conquer the planet for the Akrida, but each invasion was thwarted by the Men of Letters.

Finally prior to the 1970s, Joan latest invasion attempt saw to her exhausting her power and also wiping majority of the Men of Letters. Though the invasion was a failure, the queen and a few of the Akrida hid themselves among humanity, and slowly began wiping out the remaining Men of Letters.

The Akrida began to move towards opening a portal to the Akrida homeworld to allow the rest of their kind through. However Dean Winchester from the prime universe, caught wind of their schemes and manipulated events to allow his past version of his mother and father to meet and for the Monster Club.

The Akrida worked in the shadows to acquire monster essence to restore their queen. However they eventually became aware of Dean Winchester's existence and realized the threat he posed to their plans. Joan once she regained her strength eventually tracked Dean down and captured him. Though due to him being a spirit, she was unable to kill him and thus could only banish him to the world between universes.

The Monster Club though attempted to bring Dean back using an artifact of the Men of Letters, however they were only able to bring back his car the Impala. Since the Impala was not of their universe, it was a perfect weapon against the Akrida Queen, which Mary Winchester then used to run Joan over.

Joan's death resulted in the extinction of the Akrida, ending their threat to the multiverse.