At the end of Dragon's Keep you'll face against this boss. To defeat her you have to gather the apples from the platforms and put them in the cauldron before lighting it and damaging the Fairy God Mother's health by a quarter.
Just follow the simple paths to the first two and for the second two you'll have to follow the paths up to the glowing purple circle on one of the blocks, then stand there and another path to the next part will appear.
This is also a very good place to get the ogre meter achievements, just wait in the bottom left area and kill the witch and the two spiders repeatedly. Don't pick up the attack up either to make sure you get the largest combo possible, and thus do it faster.