The Aesiri are an alien species from a high gravity world.
Aesiri come from a gravity-heavy planet, and thus their bodies can withstand much more punishment than any other species. Bullets, lasers, and even missles are objects they can easily shrug and even withstand the pressures of the ocean with no ill effects. While the Aesiri cannot shapeshift, they can project mental holograms into the minds of others, and seemingly take others’ forms.
The Aesiri came to Earth via a comet centuries ago bringing a Frost Giant with them Frost Giant to initiate Ragnarök. However the Banshee managed to seal the Frost Giant in stasis while it was resting. Centuries later two Aesiri were held in the Global Alliance's maximum security containment facility in the Bikini Atoll. They were released by the actions of James Rinaker, a Shadoen infiltrator, the leader of the Alliance. Once freed they made their way to reclaim an artifact to free the Frost Giant. Once they freed it they merged with it and began to use it to freeze the planet, however they perished when the Frost Giant fell into a ravine of lava.
The Aesiri are notoriously sadistic and psychopathic, enjoying causing both physical and psychological torture.
- Roswell Conspiracies Episode 34: Devil Inside (1999)