The Cloud of Darkness

This right here is considered high-end content. Before going in check that your gear matches the min ilvl and has materia melded. You should also bring some food to have even more damage and hp. And don't forget to increase target's castbar in your UI settings and put it closer to your screen's center - you need to see easily what exactly the boss is going to do to react to mechanics in time. After you're done getting to know the mechs, have a look at the preparation section.