I have to agree that the hope shield on the upgrade is a very nice touch. Very creative.
The poison deck sounds great on paper but you need to draw 12 specific cards out of 30 ore more to get that amount of poison while you have to survive without any other sources of damage. Not too hard to do, but worst case scenario it just means more people may have to run purify.
However, I do think the card needs a bit more balance. Perhaps the opponent can also activate the card (either for free or for some card based on their mark) so that they might be able gain some advantage out of it or prevent you from setting up fully. As it is, it's very easy to sweep a field, poison the opponent, AND set up a massive shield.
As a side note, the potential to get rid of immaterial shields is a nice touch too, we need a way to deal with those imo.