I believe anniversary. Pap Chao ellenia x2 . you get those boxes that spit out 5k nx. If you have 2 or even 3 attackers, thats 18 bosses. Plus shao loot if you have hs maaaaaaan. Thats pretty fucking good. Plus the coins you get as well. I think for the 10th anniversary it will be even more insane so def something to look forward to. Edit: I actually forgot the boxes not only spit out nx, but also cs ws