Odds
I thought It was
1 in 20 chance non Classic
1 in 20 chance costume ( if available )
1 in 400 chance non Classic with costume ( if available )
So the odds get really weird if you lack any of the available costumes but for simplicity assume you have no 5* costumes, and no limited edition 5* heroes
90.25 % no help
09.75 % new costume, hero or both
FIN