To recieve an invitation to a higher rank you must role-play, this goes for both fractions.

So, you are starting out as the lowest rank aka, Raquia/Acheron.

To get to a Machonon/Styx rank, you must get at least 500 posts. It sounds fair.

To get to the highest ranks, you must get at least, 1000, that's for Zebul/Erebus rank.

Well, have fun and enjoy! ^___^