Towards the beginning of the dream, I was given a warning that at some point, a false version of me would appear. I was given instructions to go through a gateway to deal with them when the time came, because if I didn't, they would replace me. Later on in the dream, they appeared, and immediately pursued me. I raced to the gateway, my false self right on my heels, and I got /so close to it/, and then I woke up. For a good few moments as my waking brain kicked in, I was terrified, because I "didn't know if I'd made it" and, if I hadn't, that made me, the real person, the false self who had just killed/trapped the original forever.
additional: Though I remember it vividly, and usually type up everything from my dreams I can remember as soon as possible, the only note I have on this particular dream is the warning that was echoing in my head as I woke: "Maybe you can run for a while, but your false self will replace you eventually!"