Whoah, you got me there!

If you can bend the rules, so can I - for once ok? I'll switch your first 3 with your 7 (don't want to have too many doubles in there), so we get 1-7-3 with an extra 3:

Then, be prepared to meet Archibald, the Mysterious Night Prowler from No Man's Land with (here goes your Lucky 7): The Handkerchief of Improbability (whatever that means :) He's actually the Creator of... (to be announced)!

Any good? Thanks for joining!