Stanza 38: The seeress describes a hall on Nástrǫnd (Corpse Shore) where Niðhǫggr torments the dead.
‘There she saw wading swift currents
perjured people and murder-wolves,
and the one who seduces another’s wife;
there Niðhǫggr sucked the corpses of the deceased,
the wolf tore men. Would you know still [more], or what?
Stanza 63: The poem concludes with the final, ominous image of Niðhǫggr flying over the world, carrying corpses in his wings.
‘There the dim dragon comes flying,
the glistening snake, from beneath, from Niðafjǫll;
Niðhǫggr carries in his wings — he flies over the field —
corpses. Now she will sink.’
Stanza 32: The squirrel Ratatoskr is described as carrying messages between the eagle at the top of Yggdrasill and Niðhǫggr at its base.
‘Ratatoskr is the name of the squirrel which must run
in the ash of Yggdrasill;
an eagle’s words he must bring from above
and speak them to Niðhǫggr beneath.
Stanza 35: Niðhǫggr is named as one of the creatures that torments the world-tree from below, gnawing at its roots.
‘The ash of Yggdrasill suffers hardship,
more than men may know;
a stag bites it from above, and its side rots,
Niðhǫggr gnaws it from beneath.
Chapter 14-15(p. 17): When describing the three roots of Yggdrasil, the text identifies Nidhogg as the serpent who gnaws on the root that extends over Niflheim.
The third extends over Niflheim, and under that root is Hvergelmir, and Nidhogg gnaws the bottom of the root.
Chapter 16-17(p. 19): The text describes the various creatures living in the world tree, including the squirrel Ratatosk who carries insults between the eagle at the top and Nidhogg at the bottom. A verse is quoted to illustrate the tree's suffering.
A squirrel called Ratatosk runs up and down through the ash and carries malicious messages between the eagle and Nidhogg.
The ash Yggdrasil suffers hardships more than people realize. Stag bites above, and at the sides it rots, Nidhogg eats away at it below.
Chapter 52-53(p. 56): In the description of the halls of the afterlife, the text states that the worst place is Hvergelmir, where Nidhogg torments the bodies of the dead.
But it is worst in Hvergelmir: There Nidhogg torments the bodies of the dead.’
Chapter 75(p. 137): In a categorical list of names for serpents, Nidhogg is included.
These are names for serpents: dragon, Fafnir, Iormungand, adder, Nidhogg, snake, viper, Goin, Moin...