Ruarc is a Cú Faoil a dog native to Avalon related to Cŵn Annwn or the hounds of Annwn. Since he is a supernatural dog  he has some abilities that come with it. He is far stronger, faster, smarter and more durable than a normal dog. He is effectively immortal though can be killed if enough damage is done. However of all of these the ability that a Cú Faoil is most prized for is its ability to tell friend from foe at a glance making them incredible guard dogs. However a Cú Faoil is very stubborn and will only obey a master it has chosen. It is for that reason that when a Cú Faoil and its master grow close enough the title of Cu is given to the master to honor them for earning the respect of a Cú Faoil.

Eiltin typically wears either a loincloth or the Avalon equivalent of Compression shorts that's it. His Tattoos are made from a plant ink similar to Woad native to Avalon.