You simply wait until the 400-day countdown ends. You can speed this up by making the Shade’s home cozy (reading books, drawing, playing instruments, or keeping a fire going).
There is a variation where if you try to leave the caves and then return to wake the King after the timer has already hit zero, or if you perform certain "disloyal" acts before the end. THE LONGING - ALL ENDINGS (400 Days, Good, Bad, Secret)
While exploring the upper cliffs near the exit, there is a ledge where the Shade ponders the "end." If you choose to jump off the cliff, the Shade falls to its death. You simply wait until the 400-day countdown ends
If you attempt to climb out of the well but fail, or if you interact with the Blind Man and choose to "end the longing" prematurely by jumping, you trigger a variation of the death ending. While exploring the upper cliffs near the exit,
This ending requires you to abandon your duty and find a way out of the subterranean kingdom.
There’s something hauntingly beautiful about just sitting there for 400 days and doing exactly what you were told, even if the result isn't a 'happy' one.
Similar to the Bad Ending, but triggered specifically by interacting with the "Old Blind Man" or reaching a specific point of hopelessness near the well.