The Suicide Mission at the end of Mass Effect 2 is the most mechanically complex narrative sequence in any BioWare game — a mission where every squad member’s survival is determined by decisions made throughout the entire game, many of which appear irrelevant at the time they are made.
The survival algorithm is not visible to the player but has been fully documented by the community. Each squad member has a Loyalty rating, a Combat score, and a Tech/Biotic score. For each phase of the mission, specific roles require the highest-rated available character. Assigning an unqualified character to a role triggers their death. Assigning someone unloyal to lead a fire team triggers a death. Taking the wrong squad into the final chamber triggers deaths.
It is possible to complete the Suicide Mission with all 13 companions surviving. It is also possible to complete it with Shepard as the sole survivor. The mathematics permit every outcome on a spectrum between those extremes — and the outcomes persist into Mass Effect 3.
The most devastating single decision: after the long walk to the final chamber, you must choose who holds the line. If your reserve squad contains only one or two members, they die regardless of loyalty. The game does not warn you that the long walk depletes your reserve. Players who optimised every loyalty quest but took a small crew into the final mission lost characters they had spent 30 hours with in a cutscene they could not reload from.
This is why I always check every corner. You never know what’s been left for the observant player.
The environmental storytelling in this game is on another level. Thanks for documenting it so clearly.