Notably, because this Cases final ability can only be activated at Sorcery speed and the Case isnt Solved until your end step, you wont be able to use it until your next turn
Cards like Mycosynth Lattice or Trinisphere push Karn from irritating to game-ending, and the fact that this happens without attacking explains why he ranks among good planeswalkers, arguably one of the best to ever get printed for artifact-heavy metas
It redirects any damage it takes to another target and prevents players it damages from gaining life for the rest of the game, making it a perfect finisher for decks like Mono-Red Aggro
The second will come when trading, when something looks a bit off you should immediately start to focus more and look for other issues
For years after it was printed, it was a Modern staple in decks like Lantern Control and Affinity, but was eventually banned to slow down Affinity