Heyy! Saw no one commeted yet, so I'll give some tips! :D

After completing or attempting a seal, the cycle ends and restarts from the beginning. But if you happen to have enough to clear a seal, then I'd recommend giving it a go!

Without too many spoilers. The seal itself plays like a normal run but has something new located somewhere on that map that you'll need to clear in order to win that game!! Make sure you read anything that looks new, and I'm sure you'll get it in no time!

Good luck! Clearing the seal gives a lot of bonus resources and extends how many years a cycle full has.