This game is a little different from your typical Black Crusade game.
First, no singular warband, characters start solo. Characters also have goals they are moving towards. Progress in these goals and accomplishing them is the ultimate goal. Moving towards a goal with earn characters XP and corruption points. For players you decide how these goals are going to be accomplished.
Now for some Q&A.
Q: How do I move from planet to planet?
A: Find yourself a ship, someone with a ship, or make a deal with a sorcerer/pysker to teleport you. Approach all options with caution. The Screaming Vortex is not a nice place with nice people.
Q: What is the GMs role with the sandbox?
A: I'll be running NPCs you run into. Run NPCs in combat. Describe what happens with rolls. The usual stuff.
Q: Updates?
A: Updates are dependent on the players. I'll update the day of your action or a day after. Life is volatile though so sometimes it might be two days. If something big is happening I'll be sure to inform players about these and any delays that would rise because of it. If I don't give any reason for an absence and if I've been gone quite a while PM me.
Q: PVP?
A: You bet ya. That is if you run across another PC of course.
Q: Where do characters start? Do I choose or does the GM?
A: The GM picks the starting local for the PCs. Most will be starting on their own planet. Location threads will be broken up by planets. So, say if two characters are on the same planet they would be posting in that planet's thread and not their own individual ones.
To wrap this up. All sandbox games are dependent on a characters drive. They need to be active and pursuing what they want. There is no mission to complete but that's why I came up with character goals. A built in drive for players to accomplish for their characters.
