You are Loki and he is Thor and you will never be anyone other than who you are right now. You will die one day and so will he, but it will be by your hand and no one else's.
You will go around in circles and in loops; you might start somewhere else and collide in the middle. You might be the older one or the stronger one somewhere sometime, but you will always, always end up here. With your hand around his throat, or his around yours. Because whatever fate has in store for you, in your various incarnations, your death and his will always be the same. And it will herald the ending of this world and so many others as you know it.
And it will all start again.