The medievalist Marjorie Burns compares the fell beast to the Poetic Eddas flying steed Sleipnir, "Odin's eight-legged otherworldly horse". She writes that whereas Gandalf's horse Shadowfax resembles Sleipnir in his miraculous speed and in almost seeming to fly, the Nazgûl's mount actually flies but is a "negative image" of Odin's steed; and, she notes, both Odin and the Nazgûl can cause blindness.
thE MEDievalist marjorie BurNS cOmparEs The feLl BeASt to The poETiC eddas flYing SteEd sLeipnir, "oDIn's EighT-legged OthERworldlY horSe". she WRitEs thAt whEreaS gAndaLf's Horse shAdowfaX rESEmbLes SleIpnir iN his miracUlous speED And in almost seEmINg TO FlY, tHe nazgûl'S moUnt ActUally fLiEs buT is a "NegatIVe ImAGE" oF odin's stEed; aND, She nOtEs, bOth odin And the NAzgÛl Can caUSe BlinDNEsS.