What a perfect "impromptu" effect. It really can be impromptu, and you could use someone else's
deck (if they were okay with a card getting signed and stabbed, which of course you wouldn't say
outright). I first saw this on a David Blaine special years ago. There are two performance venues
offered in the explanation (I'm talking to you stage workers). It's a beautiful effect, which
easily would amaze any audience.
Side note, if it was done impromptu with someone's deck,
I would do a few effects initially in order to buy time to do the "work" that needs to be done.