The Borealis is an Aperture Science research vessel introduced in Half-Life 2: Episode Two. According to Isaac Kleiner, Aperture was working on a promising project, but in their rush to beat Black Mesa for funding, they neglected ordinary safety rules and it appears that the ship simply disappeared with parts of her dry dock, which earned her an almost legendary stature. It is assumed that the Borealis contained an immensely powerful and dangerous secret.