Champions should be allowed to be sold to improve roster.
people just want to be able to do 99% of a challange, and then sell the effected champ.E.g. Use a 4 or 5 star aegon with 3 star synergy team to plow through Labrynth, along with 4 star starlord... then with the Overseer at 1% health... sell the extra champs, and finish it with "only starlord".