X6-88 is an InstituteCourser, designed for high-risk assault and retrieval operations above ground. X6 is very capable at engaging enemies at range and is equally capable of direct assault and more subtle approaches.
Shortly after arriving at the Institute, Father tasks the Sole Survivor with helping to retrieve the leader of a band of raiders, Gabriel, a mind-wiped runaway synth. X6-88 is the Courser dispatched to aid in this task. Completing the quest Mankind-Redefined makes him available as a companion for the Sole Survivor. He can be found at the Synth Retention Bureau.
He will like it if you enter a power armor. Thus, you can save, load, enter power armor, and see that "X6-88 liked it". Rinse and repeat. Same goes for upgrading power armor..
He will like that you accept side-missions from the Institute despite the fact that the game doesn't notify you about it. (can be checked by clicking on him in the console and typing getav CA_Affinity before and after).
When completing the Nuclear Option, and X6-88 was not sent to a settlement, he can be found in the SRB section of the Institute after the security lockdown is lifted along with ~7 other coursers.
He is the only companion who can follow the Sole Survivor in and out of the Institute.
He will turn hostile if the player sides against the Institute.
Upon first meeting X6 for the Synth Retention mission, if the Sole Survivor does not complete the mission or go to the location, he will follow as a second companion anywhere the Sole Survivor goes. However, he will pick fights with the Brotherhood of Steel and various other allies.
He can be found at the Synth Retention Bureau area within the Institute. Depending on where you started the Synth Retention quest, he might also be in front of a fishing boat at Nahant Wharf (often he will fight the BoS patrol dropped off in a scripted Vertibird landing close by) or in front of a fishing boat about 100 yards due northeast of the Nordhagen Beach settlement, the north and south entrance to Libertalia respectively.
If X6-88 is brought to Boston Airport after the Prydwen arrives, the automated spotlight turret near the fast-travel point will track him and sound an alert even if the Brotherhood is not otherwise hostile towards him.
If X6-88 is dismissed at the Prydwen, it will cause X6 to fight with the Brotherhood. X6 will not travel to the desired location until combat has ceased.
Oddly enough, unlike the Railroad, the Brotherhood won't turn hostile if he's brought along to the Prydwen.
Despite the hostility between the Brotherhood and the Institute - when meeting Danse, or vice versa, the two will not be hostile. Even when one of them is not recruited, and they will have a short conversation with X6 even stating he is with the Institute, if the player character has X6 and tries to recruit Danse.
Compared to other companions, he is very neutral about how the Sole Survivor resolves side quests. He will often comment at the end of quests and even expresses his opinions, but this does not usually change his relationship values.
If the Sole Survivor is declared an enemy to the Insitute, X6 will become unrecruitable and will be hostile until he is killed. This can prove to be a problem if he was sent to a settlement, as he may engage the settlers.
If you complete The Nuclear Option by siding with the Railroad and without having been banished from the Institute, X6-88 will continue to be available as a companion. Unlike some of the other companions, he does not have any new dialogue reacting to the destruction of the Institute, and will speak as if you were still allies. Bringing him to the Railroad however will still cause its members to turn hostile. In this case, if you exit quickly via the door to the Old North Church without attacking any of the Railroad members, then re-enter the area, X6-86 will remain outside the door and Railroad members will revert to friendly status (even if some of the unnamed Railroad agents were been killed by X6-88.)
He will often give hints during dialogue options which can point to how he wants the Sole Survivor to answer. He will like or sometimes even love if responding accordingly. One example of this is during Building a Better Crop. If one answers Cedric with a threatening response as X6 implies they should, he will like it.
When dismissing X6 to travel with Nick Valentine, he will have a short dialogue urging Nick to watch out for "the future of the Institute" despite Nick being a "rogue" synth (as far as in not working for the Institute.) Nick will respond sarcastically and X6 will then travel to wherever sent to.
X6-88 seems to actually take pride in his status as a Courser, sometimes stating "The people of the Commonwealth are terrified of Coursers. They should be."
After Synth Retention, the Institute Coursers will sometimes tell you "Unit X6-88 speaks highly of your combat skills." and Justin Ayo will say "X6-88 was impressed with your work at Libertalia. He does not give praise lightly. Well done."
He will mention the Institute once had an all robot sports event when taken to Easy City Downs
Strangely, he neither likes it nor dislikes it if you return the Deathclaw egg to its nest in The Devil's Due. He will still comment, however.
Upon being killed by the player, he may say, "I can't... I can't..."
He appears to be afraid of heights or flying, as he dislikes boarding Vertibirds.
Unlike Nick Valentine and other Synths, X6-88 has no innate damage resistance or energy resistance and is entirely reliant on armor for protection. Despite his unusually high S.P.E.C.I.A.L. stats, his health is identical to that of all the other human companions, and he lacks the enhanced health and innate damage and energy resistance shown by other Coursers.
"Your pet's bleeding out here, maybe I just finish him off"
"Stupid animal, what were you thinking?"
"Oh great, dog's down again"
"I'm not sure the Institute needs more Deathclaws, but it's your decision." – When returning the Deathclaw egg to its nest in The Devil's Due
"I've used some of these techniques." – When brought to Pickman's Gallery
"A place for infant humans. I've only seen one once. It was unsettling." – When brought the Abandoned Nursery in Trinity Church
"If I've learned anything since we've been running together, it's this: Holy shit, was I wrong about you. You're as tough and determined as anyone I've met. Maybe more." – During his final approval talk
"Good riddance." – When dismissing Dogmeat to recruit him
When swapping X6-88 with:
Danse: "You have the training and equipment to handle this assignment. The Institute’s future will be in good hands.", to which Danse replies: "Don't mistake my tolerance of your existence for friendship, synth. We have nothing to say each other."
Deacon: "I don't know who you are, but if any harm comes to this man/woman, I'll find out, then I'll find you." to which Deacon replies: "Me? Oh, I'm nobody. But hey, don't you worry about a thing"
Piper: "Our files indicate that you have a tendency to get into trouble, Piper. Try to stay out of it from now on." to which Piper replies: "And who's gonna stop me? You?"
Cait: "I’ll be watching, Cait. If you fail to protect this man/woman, I’ll know about it." to which Cait replies: "Yeah, sure… what are you gonna do? Leak oil all over me?"
Curie: "In my judgement, you're not ready for this, Curie. I hope you'll prove me wrong." to which Curie replies: "I have survived centuries more than you, monsieur."
Nick Valentine: "This is the future of the Institute that you’re protecting, unit. Remember that." to which Nick replies: "And we wouldn’t want to do anything to upset the Institute, would we?"
MacCready: "I know your reputation, MacCready. I'm confident you can handle whatever threats you encounter." To which MacCready replies: "Uh, yeah...thanks...I guess."
Hancock: "I hope you understand your responsibilities, Hancock." To which Hancock does not respond.
Codsworth: "If you fail in this assignment, Codsworth, I will personally make sure that you are dismantled and then melted down." To which Codsworth replies: "You have nothing to fear, Mister X. I am well aware of my duties."
Strong: "You have the potential to be an excellent bodyguard, Strong. I just hope you understand your responsibilities." To which Strong replies: "Strong protect by crushing enemies."
pc If X6-88 falls into the water in Libertalia, he won't be able to interact with the player character and would not leave the water. This can be fixed by shooting him several times or proceeding alone to find Gabriel or simply advancing further into Libertalia.[verified]
If X6-88 is downed after defeating the raiders he may not be able to show up at the Sole Survivor's quarters.[verification overdue][platforms tag needed]
pc When commanding X6-88 to travel to a settlement while the player character is in the Institute, he may disappear. When using the console to teleport the player character to him via the player.moveto command, the player character gets teleported to the Institute but X6 does not appear. To prevent this simply dismiss him outside the Institute. To remedy this pull up the console and enter prid 000e210a, hit enter, then type in enable, after hitting enter and entering moveto player [verification overdue]
pc Even after the player character has destroyed the Institute, X6-88 still can be found near the Nordhagen Beach settlement and still can be recruited as a companion. Moreover, dismissing him will simply make him teleport back to the Institute SRB as if it is not destroyed.[verified]
X6-88 may be found wandering the Commonwealth if assigned to a settlement. When found he will be hostile towards the player if the player destroyed the Institute. (i.e. X6-88 was stationed at Murkwater construction site, but he left the site and was later spotted fighting Brotherhood Patrols near Croup Manor.)[verification overdue]
When found, X6-88 may be still essential, or not and may be killed.
pc X6-88 may continue following the player character even when dismissed or replaced with another follower. This prevents all interaction with the Railroad. Fix is unknown.[verified]
pc For some reason once one is able to recruit X6-88, he will be nowhere in the Institute. The Sole Survivor can find him between SW of Libertalia and NE of Nordhagen Beach, by a shored boat.[verification overdue]
pc If X6-88 is the companion when boarding the Vertibird for the Spoils of War quest and become enemies with the Institute, X6-88 will fall off the Prydwen, become hostile, and become invulnerable. This will become an issue after the quest completes, as he remains by Boston Airport and will distract all troops, including Liberty Prime, and one will not be able to continue.[verified]
pc If sent to a settlement in forehand, X6-88 will not become hostile if one completes the main questline with the Railroad. This could happen because of that one never technically became "enemy" with the Institute.[verification overdue]
If X6-88 is killed, after becoming hostile with the Institute, his body may disappear and then reappear at Nahant Wharf where you first met him.[verified]
If X6-88 is killed after the player character becomes hostile to the Institute, his body may disappear and then reappear on the beach Southwest of Libertalia, next to a shored boat. [verification overdue]