Eris is a dwarf planet. It was put into a special classification of dwarf planets, a plutoid, along with the demoted Pluto.
It orbits the Sun beyond the radius of the eight official planets, at a distance about twice that of Pluto.
Infrared images have shown that Eris is actually larger than Pluto.
While the eight planets have almost the same tilt when orbiting around the Sun, Eris is tilted 44 degrees from the plane of the planets. According to the mainstream theory of the formation of our Solar System, all space objects should be tilted the same, since they supposedly all spun out of the same disk. But there are quite a few objects that do not fit the model. Such anomalies are explained by hypothesizing that such objects collided with other objects in the past with such force that their tilt was changed. No such impacts have been actually observed, however. So design is a better explanation for differring tilts and motions of space objects.
Eris has a moon called Dysnomia. That moon circles the dwarf planet in almost a circular orbit in about 16 days.
Lawrence, Debbie, and Richard Lawrence. Our Universe. Petersburg, KY: Answers in Genesis, 2008. Print.