Board Thread:General Discussion/@comment-32974172-20171018140105/@comment-30397282-20171018193743

omg this is an old trick in japanese mobile games.

you collect specific items to upgrade your cards, something like elder kais. they are rare and you have to be persistent in getting them.

for me it kills the game coz it becomes new meta in which you have to play till the last drop of stamina points

I hope I'm totally wrong...