Mmh. If there is a "sleeping caern" and a variant rite to awaken it vs. creating a completely new one, it is not in one of my three books, as far as I can see. There also does not seem to be any hint of that e.g. on the Fandom Wiki. Would you happen to have a pointer towards this topic as well? It would sound about fitting, I concur.

Nb. the Ananasi's Rite of Spinning, which creates "something like a Den-Realm" is described in Changing Breeds but cannot easily be used as a stand-in, because a den-realm is supposed to have (at least) five quite distinct levels of extend, whereas a Sylie is always less than even a level 1 den-realm (single room vs. whole house), whereas each's other qualities are not really quantitative in nature.

Mmh, about as I feared. You would not happen to have a suggestion, which ruleset (neither of which I have access to, yet) would be easier to adapt to W20? 1e or 2e? (Going to accept the answer after the customary 24 hours.)

That looks a lot more sensible than what is on the wiki. Huh. It is of course perfectly normal that wikis for licensed work are written rather terse - and for obvious reasons - but I did not expect it to be quite so... aggressively misleading. Why, thank you very much and enjoy your bounty.