Amon Amarth has recently been uploading photos of a poster all around what appears to be Germany. If you zoom in on the photos, you'll see that the band is teasing a DVD containing both a documentary and the band's 2017 performance at Summer Breeze Open Air in Bavaria. The DVD appears to be titled The Pursuit Of Vikings: 25 Years In The Eye Of The Storm, and is slated for a release sometime this November.
Specific details aren't currently clear, but more Amon Amarth in our lives is generally a good thing overall. Expect an official announcement on the release soon.