[zelphirkalt]

Good that they also have potions, so that no poison in the world is strong enough to kill you in Skyrim (or is there one?)

[wishfish]

There is one raw ingredient in Skyrim which will kill the player. But it can't be found in the wild. It's given to you for a Dark Brotherhood quest. But you don't have to use it in the quest. Can keep it for later use.