Stars

Stars can be purchased in the altar by pawning cards of the unit you want to upgrade.

Each star provide a +5% increase to damage/heal and +5% to HP."Note: Unlike levels which increase your stats exponentially, stars increase your stats linearly but after applying level. So it kind of always scale well to your current rank. ""The formula seems to like like this: (BaseValue x 1.15^Level) x (1 + 0.05 x Stars)""So the 3 firsts stars (+15%) are exactly equal to a 1 level increase (+15%); but 6 stars (+30%) are a little less than 2 levels (+32%)."

Towers
(Values with * means the values must be verified)