The Cassandra Deck is Docc Hilford's. He just lectured here and did a couple of effects with it. (Great Lecture, by the way). It is gaffed, there are no misprinted or custom printed cards, but one-half of the cards have been physically altered. You could build one yourself, but if your time is worth anything, you'd be better off buying on from Docc. His email is email@example.com
He also sells a booklet with 64 (I think) effects using it.
The secret isn't mine to give, but Docc struck me as a very generous guy, so if you were to email him, he might tell you exactly what it is. It can be used for Tossed Out Deck, forcing, revealing a peeked/glimpsed card, many Si Stebbins effects.
It is built on "Prior Art" but is a substantial improvment.