Seeing as myself and a lot of other people were confused when they first entered the new dungeon added last week, I thought I'd make a late guide for others, when they hit 60 and are able to enter.
First of all, you need to buy a Key To The Story
for 100g. When you have entered, you need to talk to the aiM NPC and click the second option, to start the adventure.
When you do this, a lot of sprites will spawn, which you must aoe all of them that spawn, in order to progress.
Then, the door will disappear, and you're able to go through the corridor. This is the part that made me confused. ;_;
Before you enter, I'd recommended switching to a class like thief or a Lv60 Sage (if you have the class that is). When you enter the corridor, you'll be temporarily immobilized. When you're able to move again, use the skill Gallop so you have more movement speed, and run through the end of the corridor, and use Hidden Force to exit combat, so you don't die repeatedly from the sprites hitting you. ;_;
Then you will see a lot of bandits which you can kill for fat lootz (they drop Repair Hammers, Shattergems, EXP/CP charms, Eternal Power Crystals).
When you've killed all of those, you will encounter a gem. Click the rub option a few times, and a Jagged Crushard will spawn. This boss BP is slash/pierce/strike, so make sure you have a weapon that can break it.
The boss is pretty easy, so you shouldn't have any trouble with it.
When you kill the boss it will drop a Secret Sprites Treasure Chest.
Now you can exit the dungeon, and run it again, as you can enter this dungeon twice per day, just remember to reset the dungeon
before you enter again. :3