Minecraft-esque RTD is one of those concepts that has been niggling in the back of my head for months now, but I've lacked the ambition/insight to flesh it out into its own thing.
For me, one of the biggest decisions was trying to figure out whether you should have relatively preset buildings, like a Hovel and then a Hut, or Shack L3s or what, or whether it should be more literally MCish in that you can build basically whatever and then calculate out the costs and such. Unfortunately, I had to lean towards the former option because updating posts other than the each-turn-status thing is a pain in the ass.
As far as regular cosmic events, you could set it up such that X event happens every Y interval, and then set up a simple way to track/predict when such occurrences happen to intersect with other events in interesting ways. So every time the Blood Moon is full, the ravening hordes are much more ravening than usual, or a particular flavor of horde only appears on this date. Every time the Dominion Moon is full, it is easy to mind control the hordes via a particular spell/ritual. Every time these happen on the same day, players spend the night picking fights with otherwise-too-powerful enemies because they have forgotten beasts to ride around on.
Obviously, I'd need to know more about the actual mechanics to suggest what kinds of things you could get going on. It would also be groovy if joint celestial acts had altogether unexpected consequences, in addition to or in lieu of the normal effects. I'd also note that you could (nay, should!) hide this information from the players, and have astronomic tomes be one of the rewards of exploring the world- it would certainly pay to know when to avoid outdoor excursions because the Stars are Right.
I do like this stuff. The only issue is that then it'd be getting towards being a pain to keep track of, since instead of just incrementing the season counter or whatever I've got to look up the progress of five different celestial bodies, increment them all, ponder just how these effects interact, and so on.
Of course, this is more an issue for innate effects, like more monsters coming out. Stuff like easier rituals of a given type are a bit easier because I only have to look them up when the players try to use them. I guess if I was dedicated I could also just come up with a little calendar to glance at and figure out if there's anything special this turn.
I also do like the notion of the players knowing nothing. I think I'll be going with trial and error and brutal, brutal experience for figuring it out though, rather than books. I suppose friendly tribes or rare cases of lost knowledge might also give you hints. Like, I would kind of assume everyone would know about a ring of death showing up every month or two. That tends to be a thing.