User blog comment:B214/Volume 23 discussion blog/@comment-190.160.185.214-20170321211038/@comment-87.9.174.130-20170321224333

Tannin standing on 2 legs was only a anime/manga thing, in the light novel is assumed he he use 4 legs, even because it was stated that Grendel was the first dragon seen standing on two legs (not counting the one shapeshifted into human form like Crom Cruach or Tiamat)