There's a lot of material in the very NSFW post at Sankaku Complex. It includes the original ecchi manga (which was cancelled), together with very badass Pierrine (who thought!), and a few other tidbits. The one I found notable was Helma Lennartz, a jet witch (she flies a Me-262). Both mangas feature animal familiars, present in the OVA, but utterly absent from the TV series. Steven mentioned that "the shield is a function of the Striker Unit, not something that witches inherently can do". I don't know how he figures that, I must've missed that part of ep.5. But it seemed that the animal created the shield in the OVA, and perhaps in the manga too.