Solved Amount of people in game?

You will have to create 8 different accounts if you wish to fill a whole 8/8 game by yourself. You may use 8 different characters that belong to the same account too but you will be kicked out to the login screen every time you leave the game with your character so having a separate mule account is more recommended because of this.
Baal games are very popular around here and they tend to get full extremely fast, sometimes within seconds but if you wish to host solo baal runs and get the maximum experience out of them then you are free to run multiple instances to fill the game. The option where you can set your game to full through a command only works in single player.