Karn - Can withstand planeswalking

He had hardly spoken the words when, with a sudden, vertiginous whirl of movement, the cliff top melted away. The scarlet sea and sooty sky disappeared as well.

Karn stood still. Urza was planeswalking them into the aerie. A human could survive that trip only by being carried in a protective embolism, or turned to stone, or made a flat creature of immutable geometry. Karn merely rode as he was. Urza had sent him on more troubling journeys.

They arrived. The sooty sky remained above. The rest of the world was replaced by a vast, woven bowl of wood and clay, the lair of the fire drake.

***

Time Streams, Chapter 13