Maybe as you venture through the galaxy you start to find artifacts of some long dead or ascended
race that you can use to uplift your species.
One the similar note. One idea i got that could add some story to the Thrive.
Maybe some species has ascended before your’s (which could be humans), and you ca collect artifacts to create new theologies or even use to build ascension gate(s).
I think Stellaris is a good example of various artefacts you can find on other planets - many of the anomalous features you can research on other planets are from ancient aliens. Ruined structures, remnants of battle, the list goes on.
Decayed spacecraft/megaprojects are another common feature - some are autonomous and still function (often hostile), others can be repaired.
I don’t think alien artefacts are all that important in theological development, especially if they are comparable to your own tech level. Finding an arcane object in space stage vs when planetbound has a different importance.
What I meant is finding an space-age (or even ascension) level artifact in Industrial Age, or in space-age finding an ascension artifact.