Loki’s Castle lies midway between Greenland and Norway, around 2,300 metres below the ocean surface. It’s a field of hydrothermal vents—black, rocky chimneys that belch out volcanically superheated water. And yet, despite the hellish landscape, life abounds here.

Now, fifteen kilometres away from the vents, a team of scientists led by Thijs Ettema from Uppsala University have discovered a new group of very special microbes. They are the closest living relatives of all eukaryotes—the huge group that includes every animal, plant, fungus, and all other complex life on the planet.

Ettema named his new microbes the Lokiarchaeota (low-key-ar-kay-oh-tuh), partly after the vents where they were found but also partly after the Norse deity whom the vents were named after. Loki was