Part 5/9:
This reveals Tolkien's use of retroactive continuity, or "retcon," a literary method wherein previous facts within a storyline are altered or redefined. Isaac expresses a preference for retcons only when they originate from the original author, in this case, Tolkien himself, asserting that these changes are indeed canonical.
The Fate of the Seven Bogs
With the understanding that there are seven Bogs in the finalized narrative, we must explore their fates post-Gondolin. The most notorious of these, the Perdition of Durin, represents the risks and consequences associated with awakening such monstrous entities. This Bog lay dormant in the depths of Moria for centuries until accidentally awakened by dwarves, ultimately leading to the devastation of their kingdom.