Malmuria

The Malmuria are an alien species native to the "tenth planet" Malmur, which occupies a highly elliptical orbit in the Solar System. The Malmuria raid Earth for food once every 2,006 years, when Malmur passes by Earth.

Anatomy & Physiology
Malmuria are highly unusual creatures of recent aquatic ancestry. They have a black, ovoid body roughly the size of a human torso, with a cluster of ten tentacles emerging from each side. A third set of ten tentacles sits at the bottom of the body, which the Malmuria use to walk. Malmuria have ten eyes, each one on a retractable stalk that can be withdrawn completely into the body.

Biochemistry
Malmuria breathe methane in place of oxygen. They can consume the same kinds of molecules for food that Earthly life does, although they must modify them first in unspecified fashion.

Diet
Malmuria are omnivores. Due to their homeworld's devastated state, they feed exclusively on paste made from organic matter harvested from Earth.