Heimdall is an ice/ocean exo-planet, one of three planets orbiting around a Type K star. This is the alien's home. The alien has certain traits that help them move through the thick, slushy water of Heimdall.
Life on Heimdall first sprouted from the trapped water in Ice VII crystals (an exotic ice that don't freeze or melt the same way earthly ice does). In Norse Mythology, Ymir was the first giant born when the ice of Niflheim met with the heat of Muspelheim. Ymir came from drops of water, and so is a fitting name for the alien.
Ymirovskites don't breed or die. They roam the dark oceans ranging from the size of an ice fractal or that of a giant squid.
Heimdall has high pressure atmosphere, so the temperature is fairly uniform around the planet, meaning there's not much biodiversity.