Hello, I just read dominion splinter from Halo - Tales of slip space. I am know left to wonder if I should know who or what Durendal is in the Halo universe after Cortana mentioned it’s name. I do know that it is an AI similar to Cortana in the marathon universe and it made me think that it could be a nod to that. That being said, it would be odd in my opinion to use the name Durendal in the context it is used in and just consider it a nod to an old bungie game.
There wasn’t any other topic about this and I have not seen videos covering this specific topic so it seemed to me that I am just missing something important here that everybody else knows.
Frank O’Connor, you wrote the script, feel free to enlighten me on the topic if you see this 
You’re quite right about it possibly being a nod to Marathon. Beyond that, I believe it’s part of the “Hunt The Truth” Mystery of Dominion Splinter (DS) and Halo 5. In the absence of a reply by Frank O’Connor, here’s my take on his crafty story…
Below is the story of the sword Durendal, as linked in the phrase from Norse Myth “I am Cortana, of the same steel and temper as Durendal and Joyeuse” from which Cortana gets her name. In the same way, the “Cortana” in Dominion Splinter first likens herself to Durendal, and then at the end says she will do something “Joyous” (i.e. Joyeuse). So for Frank O’Connor’s puzzles in DS, he contrasts the idea that Durendal was thought to be “unbreakable”, yet the related Cortana Sword had its tip broken off, and AI Cortana could break herself into fragments - a contradiction, or a lie in the DS story about her being an “broken off fragment” of an “unbreakable” thing?
But in the article below, also spot the image in the “Local Lore” section of the “alleged fragment of Durendal” as being the image used in Dominion Splinter in Marco Rudy’s artwork. But that sword is an imposter (!!!), actually being “The Sword of Rocamadour” which is a replica of Durendal, complete with “the chains my makers have shackled me with” as “Cortana” claims in DS, and so the Rocamadour version of the Durendal story that this supposed “Cortana” quotes in DS is actually false and made-up by local Rocamadour Monks in the 12th Century.
So, when this “Cortana” claims “I am Cortana, of the same steel and temper as Durendal” but shows us the imposter Sword of Rocamadour, doesn’t that also imply she also is an imposter and “an alleged fragment of Cortana”? This then matches the hidden clues in Halo 5 that this supposed “Cortana” is an imposter.
As the Warden says at the end, this “fragment” wasn’t trying to get in, but this “Cortana” was already in the Domain, and sent this fragment out to talk to the Warden who (far too late) realises “You lied to me! You’ve just been stalling me” (with made-up stories to distract him so she can hack into and control him).
Of course, of the three swords of Cortana, Durendal and Joyeuse, ultimately, the sinister implication is that Durendal was a “weapon of mass destruction” (WMD), and if she’s like Durendal, then this alleged “Cortana” must be a WMD Cyberweapon!
https://en.m.wikipedia.org/wiki/Durendal .
So, perhaps typical of Frank O’Connor, the story of DS about a “Cortana that turned evil for no apparent reason” is like one of 343i’s jokes about other “mythological creatures that don’t exist” like the Unicorn…
https://www.halopedia.org/Unicorns .
Finally, since Durendal was the sword of the famous French warrior Roland, AI Roland in Halo 5 and the wider EU is probably named after him and linked to these ideas:
https://www.halopedia.org/Roland .
Hope this helps. 
Thank you very much for the detailed answer, I did explore most of the information you mentioned but I learned some things from your post. If I understand completely what you mean (English is not my native language) you think cortana is just quoting durendal from the song of Roland and not marathon, and she is talking about Durendal as a sword from the story rather than something from the Halo universe.