Places in Middle-earth
Region: Beleriand & North
Meaning: According to HoMe V: Mountains of Duress, according to HoMe XI : Mountains of Oppression
Location: Above the dungeons of Angband, these three peaks were in front of the Iron Mountains.
Description: Thangorodrim is three peaks or 'towers' raised by Morgoth, "mightiest of the towers of Middle-earth."
The Silmarillion, Ch 13, Of the Return of the Noldor
But above this gate, and behind it even to the mountains, he piled the thunderous towers of Thangorodrim, that were made of the ash and slag of his subterranean furnaces, and the vast refuse of his tunnellings. They were black and desolate and exceedingly lofty; and smoke issued from their tops, dark and foul upon the northern sky.
The Silmarillion, Ch 14, Of Beleriand and Its Realms
From the description of the Nirnaeth Arnoediad in Ch 20 of the Silmarillion we know that there were "many secret doors in Thangorodrim."
It was on Thangorodrim that Húrin's chair of stone was set, and likewise there that Maedhros was chained by one hand.
Thangorodrim was destroyed when Eärendil slew Ancalagon, and the dragon fell upon the towers which broke beneath him.
Contributors: Lyllyn 5.20.04