If you enter the nether/beat the ender dragon for the first time on one save, exit that save, and then enter the nether/beat the ender dragon for the first time on a different save; the "You have released the ancient spirits"/"Impending doom" message does not appear the second time round.

This bug only occurs if you do not restart Minecraft for this whole process, if you restart Minecraft at any stage in between entering the nether/beating the dragon for the first time and the second it will play the message both times.

The bug will also occur though if you load a save where you have already entered the nether/beaten the dragon, exit that save, and then enter the nether/beat the dragon on a different save. Again, only if you don't restart Minecraft in between.

Tbh I can't see this being an issue for anyone other than speed runners so it's not a massive problem and definitely won't be for me personally, only noticed it while testing for a modpack. :)

Thanks for reporting that! It was serious issue because game state wasn't changing when loading different worlds. It will be working as it should be in the next update.