Guide covering floors 46 thru 48, failed on 48 due to lack of practice sadly!
Coverage for 49 and 50 may or may not come in the future, I don't typically like to do full runs so it may not be until after the Evan Revamp.
Floor 47 Map: http://imgur.com/lZi3Hal
Floor 49 Reference List: http://strategywiki.org/wiki/MapleStory/Towns (select a town / area to see all the related mobs and how to spell their names)
Some short notes about 49 and 50, 50F I feel is pretty self explanatory, and you'd probably learn more about it by watching a video of your own class fighting Dorothy than you would learn from me explaining it.
49F is another quiz, you're shown a variety of blacked out mobs and are asked to name them. You can click on most mobs to see their name listed in the Codex, but for mobs you can't click I included a link in the description with a wiki reference that I use for 49. You can basically go on the wiki and select any given town / area in order to see all of the mobs and their names, so that can help you figure out the correct answer if you're stumped. You also get 1 skip, but try not to waste it because some mobs look very similar so it's best to only skip ones that you absolutely cannot figure out.
