This post will offer some ideas for fleshing out the Forge of Spells. Of course, the PCs don’t know that the forge has diminished in power until they get there, but when they finally do it’s anticlimactic to say the least.
As the adventure is written, the consequences of Nezznar seizing control of the Forge of Spells is negligible.
To me, however, this greatly reduces the campaign’s stakes. The underwhelming nature of the forge is likely an attempt to “nerf” it so the party doesn’t have access to a potentially never-ending stream of magic weapons. Apparently, the power of this brazier/forge has “waned over the years, to the extent that it can no longer be harnessed to permanently enchant magic items” 2. Instead, we get a “small brazier in which an eerie green flame dances and crackles” 1.
When we reach the forge of spells in Wave Echo Cave it’s far from the legendary MacGuffin that the players have been led to expect.