Failure, death and recovery
Kessen can lose a fight. Failure changes the run without deleting the crowd's only hero.
Kessen can fall
Damage, failed saves and defeats are resolved normally. Xarnak cannot protect him from a bad result.
A wipe ends the attempt
When Kessen can no longer continue, the current fight and generated map close and the game finds a safe refuge.
The story continues
Kessen returns at that refuge. He is never permanently deleted, but the defeat and its consequences remain part of the record.