Learnerheart in the simplest words is a cheat mod, allows you to level very, VERY quickly. It makes game a lot easier yes, but on the other hand, you can note that the game mechanics of Lionheart itself spawn more enemies when your character level is higher and also when travelling through crystal teleporters your character will encounter more powerful opponents of much higher level.
New perk ranks for:
Mark of Fire
and many, many more! Changelog here: Moddb.com