You tell Lie to get #6, Backends, and #11, Ski11les.
In less than a planckth, Lie brings you your two elves. How he got Ski11les is another story, but for right now, he must've found that cat and brought him here.
You give the book you've finished writing to Backends . You then instruct her to take the book to your old universe, and to put it in the designated mailbox. You also instruct her to take the cat there, as it is easier, and the cat's travelings through the universe was already destined, you specifically remember that.
Backends pets Ski11les and disappears to sometime in your old universe to put the book into the mailbox.
You also chose her because it is the past, and she moves things in the past, hence her name.
You now rear up for your next conversation, you wonder with whom...