I Like all theories so far. I believe the narrator meant 11 including Loba so their would be 1 missing legend aside from revenant.
And and would be on of the following.
Gibraltar, bloodhound or octane. As no one directed speech to them nor they spoke.
I would say bloodhound as they dont seem of the type to be in a social gathering with the other legends, also the letter in very good English and I don't think they are able to do it.
But the that's not a really big deal.
I suspect the narrator to be crypto.
The reason is that their goal is the same revenge against the syndicate. As we know the syndicate kidnapped/killed his friend. He still need to find her and also destroy the syndicate so keeping revenant alive or in the games is for his benefit.
2 more clues I find that that points towards crypto.
In "All the flirting and douple entendres and "je ne sais quoi"... are they falling for this crap? I expect that from the men, but scanning the room, the women have taken the bait as well
They're all idiots.
For obvious reasons, I'm not affected"
He is the one with scanning abilities, and must have information regarding Loba and that's why he wont fall for her charm
After the narrator wrote and "I kept our promise " another line in yellow which indicate speech is "I didnt tell you" which means the letter was handing over to revenant in person and crypto is not a guy to be afraid or scared from revenant to give him the letter directly.
.
On the other hand I think caustic also. He thinks of him highly and more intelligent than any one else. So he wouldn't fall for her charm. And as she knows his secret so he have a motive to get rid of her.
Octane but for one silly reason. Adrenaline rush. He would love to see conflicts goes. So informing revenant will just make things more interesting.