As you progress along in the United Colonies quest line in Starfield, you will eventually reach a point where you need to infiltrate and complete missions for the Crimson Fleet. In one of your first missions with the fleet, you need to go down to a former prison called The Lock with a man named Delgado, the leader of the Crimson Fleet, and Mathis, a fellow recruit like yourself.
The point of this mission is to see if you and Mathis have what it takes to be Crimson Fleet pirates, but it’s also to try and find some treasure. The Crimson Fleet’s founder, Jaspen Kryx, supposedly left behind treasure, called Kryx’s Legacy, when he escaped from The Lock prison over a century ago. Delgado is desperate to find it, and at some point during the mission, Mathis sees an opportunity to take Delgado out. He just needs your help to do it.
The question is, should you actually side with Mathis and usurp Delgado’s role as leader or stay loyal to Delgado?
Should you side with Mathis and kill Delgado in Starfield?
The first time that Mathis brings up the idea of killing Delgado is when you are both trapped in a room after some ice covers a doorway. Mathis floats the idea of stealing Kryx’s Legacy from Delgado and then killing him so there can be a new leader of the Crimson Fleet.
Luckily, it really doesn’t matter what you say here. Whether you agree or disagree, Mathis will eventually either chicken out and not want to kill Delgado or get mad that you didn’t go along with his plan. Mathis gives you a couple of chances to agree to his plan, but you won’t ever have the chance to kill Delgado while you’re at The Lock prison.
After fighting your way through The Lock and escaping on a prison ship, you will return to The Key and have to debrief Delgado on what happened. During this dialogue, you can recommend that Mathis leave the fleet or stand up for him and say he did a good job at The Lock. Whatever you say will happen, and you can meet with Mathis on The Key to discuss his future.
If you recommended Delgado fire Mathis, he will be extremely upset with you and vow to exact his revenge. However, if you stood up for Mathis, he will be eternally grateful.
So, in the end, there are no consequences to siding with Mathis in Starfield. You will never have to kill Delgado, and Mathis is not a plant sent by Delgado to test your loyalty. I recommend just disagreeing with Mathis the entire time, as he can be kind of a jerk. The choice is yours, but it doesn’t matter either way.