About challenge dungeon

Does anyone have any idea about challenge dungeon? I mean what are the difficulties for, higher diff=more points? And how many points to promote or what is the condition to promote to the next rank?

 

I dont think much about challenge dungeon mechanic but, the reward is kinda nice, avatar ticket pieces and orb shards (at good rank). In order to get to Platinum rank, you need to participate in dungeon on every week, as for me, i m often stuck at Gold rank, if my game partner and i managed to enter Platinum rank, we will kicked back to Gold rank on next week. Side note, its better to have at least 3 party members. Since last year, lovesong been dominating the first place on Platinum rank, "50 orb shards on first place on platinum rank".

 

Thanks, at least there is someone who still enjoy a forgotten feature