Midgard

1000 years ago, a group of Norse settlers were kidnapped by alien slavers on their way to Iceland. They managed to kill their captors and take the ship, but were stranded with no way of knowing how to get back. They have spent their exile building their strength and fighting a near constant war with the slavers, known as the Jotuns. By shear luck, a scout ship has stumbled upon Earth, bringing us into this galactic conflict.