There are plenty of hints in-game that closing the Worldwound isn’t a simple procedure. We’re told multiple times, and it’s available in a lot of books, that all attempts to close the portals have failed and that normal magics to do so aren’t sufficient. We’re told at one point that capturing Iz, where the portal was opened, may shed SOME light on how to close the Worldwound for good, but even that is no guarantee. The idea of researching the notes of Pulura, that were studying the Wordlwound, makes perfect sense. The idea of researching Areelu’s notes on it make perfect sense. The idea of researching the crystals that give you your power makes perfect sense.
The fact that NONE of those actually TELL you anything, and especially that you’re REQUIRED to use results from one of them (the date), makes no sense whatsoever. A GOOD secret ending would have told you:
The Worldwound is weakest on certain days.
The Worldwound is tied to souls, but enough power could separate that tie without destroying the souls
The Nahyndrian Crystals and their power can be separated from the Abyss that spawned them
Enough fresh Nahyndrian Crystals (5) can combine into one larger and MUCH more powerful one
And the PLAYER should be required to figure out that: If I enter in those days when it’s weakest, with enough crystals to combine into enough power, I can separate our souls from the Worldwound itself, collapsing the worldwound and saving us all. Leave it to Areelu to add in taking up the realms of the abyss.