This guide may be of use:
Promyvion - The Emptiness - Get your game on I agree completely with Tiffie. The Promyvions are a bit of a challenge, but being well prepared and working together as a team makes the whole thing very easy.
The most important thing is to have Anima. Go into Promyvion by yourself, or with a partner. The bottom floor is full of Easy Prey mobs that will drop Recollections which you can turn into Anima, which you should be able to solo or duo with few problems. If each person in your party has just one or two anima, it can turn the boss fight into a complete joke. Each Anima enfeebles the boss, preventing it from using certain attacks, or causing it to run around for a good 20 seconds. 6 People x 3 Anima means you've got a good 5 or 6 minutes where the boss cannot attack properly. In most of the runs that I've done, we've only had to use about 3 or 4 anima at most before the boss is defeated. With a well-prepared party, you won't need any anima at all, but it really helps, and does make the battle a lot safer.
One thing I must strongly recommend, however, is that you
not go in with an alliance. You can't take an alliance into the final boss battle anyway, and usually an alliance ends up causing more problems than its worth. 18 people rarely agree on anything, don't usually work together very well, and no matter how much you try to get people to pay attention, someone always catches aggro at the worst possible time. Then everyone feels overconfident (We have an alliance! We are invincible!), fights poorly, and people die.
A single party should have no problems defeating any of the enemies in each Promyvion area. And a single party is much more likely to make it to the spire without incident, and is more likely to stay oragnized and avoid unnecessary aggro.