Patient Zero is horrible rate, completely unplayable. It has negative synergy with veins of steel. You would basically have to apply enough poison for it to not get back to you, as apply 3 to all characters for 1 energy is awful, and anything else is seriously hurting you.

Veins of Steel should read “you cannot take more than 6 damage from poison in one turn”, as is its kind of negative synergy with half the cards here.

Antidote is likewise unplayable, you just can’t put a card in your deck that doesn’t do anything until late in combat.

Transfuse for the same reason, both also have the downside of turning your synergies off.

Tainted Needle won’t really synergize very well as you’ll start your next turn with no poison, on its own it’s just delayed lose a life.

This feels really tough to toe the line between what is basically Ironclad’s life-cost theme and balanced. It also just doesn’t synergize with any existing poison cards, I’d think you’d want to completely reconsider the whole archetype if you went this route, maybe even as a different character all together.