I think it’s so interesting that Thistle sealed the Winged Lion away because it’s undoubtedly the reason why he was able to keep the dungeon going for 1000 years. And the thing is I don’t think we really know WHY he sealed it away, and he might not either!

He grows distrustful of the demon, like we see here, and at some point after this (and having more of his desires eaten, which we can tell by the WL’s increased size…) he seals it away. And knowing that he’s totally willing to do things like stuff his own grand nephew in a doll for going against him, it’s not like doing something like that is against his character. But, still. The fact that he just so happened to stumble upon the action that would allow him to prolong the kingdom’s existence as part of the dungeon is… interesting. Hell, even the Winged Lion is surprised that Thistle apparently did this without knowing that the demon ate desires:

This is just a hunch, but before taking Delgal into the dungeon and smashing the statue he talks about investigating the ruins a lot. And we know he does a lot of research, too. Could it be that he actually stumbled across the truth of the demon, but had the desire to do anything actionable with that knowledge nibbled out of him and forgotten about? But somehow, still had the overwhelming feeling of distrust in what the demon was saying?

He knows the Winged Lion lies and manipulates people, and yet he lacks the willingness— or perhaps, the capacity— to reflect that back on his own behavior. It’s fascinating, and makes me wonder how long he would’ve lasted if not for sealing it away. It could’ve been simply the same kind of lashing out we see him do towards the people he distrusts that serendipitously turned out to be the right move in this circumstance, or it could’ve been something more. Honestly I’m not even really sure what I think, I’d be interested in hearing other’s interpretations!