If you sell a Champion and later pull them from a crystal again, the game treats it as a new Champion. You lose all your signature levels, arena history, and iso-8 rewards from duplicating.
: Once a champion reaches their maximum signature level, further duplicates provide "Max Sig Crystals," which contain even better rewards like extra shards or rare items. Are There Any Exceptions? how to sell champions on marvel contest of champions
Duplicating champions is the primary source of class-specific Iso-8. If you sell a Champion and later pull