One theory I keep seeing is that when Kabr entered the vault, there were other guardians with him ( my guess would be a Hunter and a Warlock, which would explain the other classes raid armor in the vault ). But then gorgons erase the other two from existence before Kabr can send word of what's happened in the vault to Pahanin. Kabr is alone, but he knows he must have had help to enter the vault. " no one was with me, but I was not alone. " Idk my personal theory is that it was a past, present, and future versions of Kabr that opened the vault, since time and space begin to fray at the VoG. As far who he is now, I think he was either absorbed into the universal vex mind, or just a part of the relic he poured all his light into.