Karn, Silver Golem neuters equipment voltron, enables a few combos, lets you take out your opponents' artifacts in response to a board wipe (much like Kamahl, Fist of Krosa or Jolrael, Empress of Beasts can take out lands), kills 0-cost noncreature artifacts (Mana Crypt, Clue tokens, artifact lands), and can let you kill people with your mana rocks. He also blocks really well.
Two Score, Minus Two or: A Stargate Tail
(Image by totallynotabrony)
Two Score, Minus Two or: A Stargate Tail
(Image by totallynotabrony)
Two Score, Minus Two or: A Stargate Tail
(Image by totallynotabrony)