In Norse mythology, Nidhogg ("tearer of corpses") was the monster that ate the roots of the World Tree, Yggdrasil and swore at the eagle living in the tree's branches. Nidhogg also ate corpses.
... largest river in the world by volume, the Parana[?] with its impressive Iguaçu[?] falls, the Rio Negro, São Francisco[?], Xingu, Madeira and the Tapajós[?] ...