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.
The Furyheart version of the mod, to level up to the maximum character level 280 only 288 XPs are needed.
This file (applies also to Learnerheart and Furyheart) can not be downloaded.
Here's a link to all mirrors: Moddb.com
Sometimes Mod DB servers/mirrors are grossly overloaded and downloads display "not available via any mirrors" error messages.