The endgame interface where you can see who are currently building their final wonder and their progress. You can easily locate them on map with the "Visit on Map" button.
Endgame is the final effort in 8Realms where the player who successfully defends their building Wonder for 24h is the winner. Everyone else can attack the wonder construction site and if successful, the 24h timer will reset. If the construction is delayed long enough, more players will reach this stage and eventually one has to succeed.
After this, the game is over and the server is reset.
In the Beta version, this was triggered at the end of Modern Age but in the final version, this will probably occur in Future Age.