@durin , you said that we have rolls not only for enemies but also for possible allied forces arriving to Avernus...
1. Cypher could arrive this way or is he an enemy?
2. Could this backfire on us (for example the Dark Templar´s fleet arrives and attack us for heretics)?
4. What are the Marine Chapters that are the most probable of reaching us that way?
4. Is there any chance of getting the Mars shipment that was coming for us?
5. How high or low the chances are that allied forces actually arrive here?