General

It was essentially a theme dungeon which gave a static 10~15% experience per run, which varied depending on the quests you accepted therein. Because of this, it was extremely beneficial to late-game players looking to level quickly. It also gave out maple equips for... some reason...

It's basically a linear string of rooms with various objectives which awarded you a chunk of exp and "Friendship Points" for clearing which, when applied to the corresponding Pillar of Heaven, made stat-boosting totems available for purchase for a generous amount of mesos, but the allure was that you could buy an unlimited number of entries if you were willing to pay a fairly small amount per key in the Cash Shop, allowing you to farm exp and Friendship Points with little to no effort.

Gives lots of exp.

a place where there are bosses (well not high lvl bosses that u expect) but u get exps and i thought red leaf high is gone already o.O and its also know as a dungeon

Basically "Get to level 200 super super easy mode!" if you are willing to pay some cash. Otherwise, it's just a great time for anyone wanting to get 200 with those free daily runs.