A game I've been playing for a while now.
You should check it out! ;D
It is an idle/active clicking game where you kill monsters to gain gold and then buy "heroes" that will boost you DPS.
You will also kill bosses every 5 levels that will give you extra gold for it, but after level 100 you will get something called "Hero Souls".
And by each Hero Soul you get, you will get a 10% increase of DPS and click damage, but be aware! You can get extra boosts by buying "Ancients" with those hero souls, that means you will loose that DPS and click damage bonus but you are then boosting other stuff.
But you also need to do an "ascension" to get those Hero Souls.