Canticle is a dragon or other powerful being’s egg. The entire planet is an evenly rotating massive investiture sink. I can easily seeing that being a major part of the development of a dragon, both heating and sustaining the embryo. The hostility of the planet is also likely in part a defense mechanism.
I’m much more in the camp that it’s something Whimsy created. I wouldn’t be surprised if era 4 timeframe we see a bunch of weird space things in the cosmere that were done by Whimsy.
That’s a pretty good idea too. I suppose jumping to certainty that it’s an egg birthing a new being was hasty but it definitely seems egg-like, even if it’s to nurture a being back to strength.