Monkshood: Aconitum nagarum, dark purple form. I can't pin down a variety or a source for seeds, sadly. You will have to do a bit of sleuthing if you want one. Excellent for a poison garden; not so good if you have kids around.
WOLFSBANE: a toxic also known as “Aconitum”, flowering plant that can be used to repel Werewolves if great care is taken in its usage; an excessive amount actually increases the chances of savage transformations.
10 Lethal Plants That Are In Your Backyard Right Now
The herb Aconitum (/ˌækəˈnaɪtəm/ A-co-ní-tum), also known as "The Queen of Poisons", Aconite, Monkshood, Wolf's Bane, Leopard's Bane, Women's Bane, Devil's Helmet or Blue Rocket, is a genus of over 250 species of flowering plants belonging to the family Ranunculaceae. Aconite can kill you by stopping your heart. Touching it without gloves can poison you.