A reference to the power of Morgoth that swept southwards across Beleriand during the later First Age. For centuries after his return, Morgoth had been held at bay by the Siege of Angband. The Siege lasted until I 455, when Morgoth launched the Dagor Bragollach, the Battle of Sudden Flame, that swept away his besiegers. From that time forward, his forces advanced inexorably across the lands of Elves and Men, laying waste to their cities and strongholds and extending Morgoth's Dark Hand across the land. The Dark Lord's ultimate victory appeared inescapable until the War of Wrath, when the Valar intervened in the affairs of Middle-earth. Morgoth was captured and expelled from the world, but the War to defeat him left the lands of Beleriand ruined and consumed by the Sea.

The term 'Dark Hand' for Morgoth's power is seen only once, in Beleg's comment about Dimbar quoted above. This passage happens to exactly replicate one from The Silmarillion (appearing in Quenta Silmarillion 21, Of Túrin Turambar). Curiously, while the two passages are otherwise identical, The Silmarillion's version speaks of Morgoth's 'Black Hand' rather than his 'Dark Hand'.

This change implies an editorial decision to update the text, though lacking the original material behind this passage it is difficult to speculate on the process behind the change. Perhaps the original 'Black Hand' in The Silmarillion was an error, and The Children of Húrin took the opportunity to correct this. If so, however, it seems strange that the 'Black Hand' appears several times in both books, but the 'Dark Hand' is only seen in this unique amended case.