Blu-Ray, DVD, Video
Houshin Engi has been released on multiple video formats, although Senkaiden never saw a blu-ray release. The newer Hakyuu Houshin Engi has excellent quality blu-rays, but Senkaiden isn't left in the dust. It sports some extra videos that even contain unique animation.
Senkaiden - Viz Media DVD Release
Viz Media released the DVDs individually, as well as in a box set featuring the Volume 2 box art. The DVDs included paper inserts (a single page) that detailed Paopei, where the names came from, etc.
Senkaiden - Box Set Releases
While there seem to be many box sets, the majority of them are bootleg. This makes it hard to decide what's going to be listed here. For now, the Viz Media release included a box set. There was also a limited edition box set released in Japan that included manga designs drawn in the anime style, as well as some limited discs that included things like image songs. Note that this is just a box design, not a new series.
Senkaiden - Encyclopedia VHS
There were a couple VHS released for Senkaiden Houshin Engi, called the Encyclopedias. While they don't actually include a ton of information, they do include unique animation. Several short scenes of a specific character, who narrorates the rest of the video. They mostly consist of narrorated clips from the anime.
Hakyuu - Blu-ray & DVD: First Press Ltd. Edition
Hakyuu Houshin Engi began releasing DVDs and Blu-rays very shortly after their release. While ordering from specific stores gave certain benefits, all First Press Limited Editions so far have been released with a booklet and an additional disc. For the first volume this was the OST: Volume 1. The booklets include character reference art, a bit of an episode recap, clean versions of the backgrounds, and sketches of some of them.
