Hallatar is comprised of Swallow the Sun and Trees of Eternity guitarist Juha Raivio, Amorphis vocalist Tomi Joutsen, and former HIM drummer Gas Lipstick, and is to be seen as an extension of the doom supergroup Trees Of Eternity (Swallow The Sun, Wintersun, October Tide, etc.).
The band just released its debut single "Mirrors," which is based off of poetry written by the now-deceased Trees Of Eternity frontwoman (and Raivio's parter) Aleah Liane Stanbridge, and it's exactly as gloomy and angry as you'd expect a song in mourning to be.
You can grab a digital copy of "Mirrors" here.