Final Fantasy 11: Promyvion - Dem

Inside the crags is access to something called the Emptiness. It's a dungeon run that's part of Chains of Promathia. I loved running the Promyvion dungeons. I have never seen anything like it in any other game. I was unable to get into the room to fight the boss again. According to other players, fighting the boss is something you can only do once unless you help another player who needs to defeat the boss for the missions.

https://ffxiclopedia.fandom.com/wiki/Promyvion_-_Dem

Get the game on Steam: https://store.steampowered.com/app/230330/FINAL_FANTASY_XI_Ultimate_Collection_Seekers_Edition/

I recommend playing the game with a free launcher called Windower: https://www.windower.net/

I used this online guide to complete missions & quests:
https://ffxiclopedia.fandom.com/wiki/Main_Page