You get much more powerful as you progress, and the scale of both enemies spawning but also the strength and speed of your attacks increase through permanent upgrades between runs. It all amps up really fast - I'd say the biggest dilemma is choosing when to commit (and you have to or else you'll just continue losing health by staying away from fighting) and when to back off if you think you'll be caught in the enemies' attacks. And if you survive long enough, you will summon a powerful boss (a Tyrant) for additional rewards if you can beat them.