Recently pvp has been added and has become a big hit. I noticed then when you try to hit some players it won't hit them. You can use /fly, /god, /heal, /speed, etc. inside of the arena. You can also die at /spawn when you enter the lava portal to pvp if you don't have /god on. Recently I was out of /god mode and was trying to hit someone without a rank and they wouldn't take damage. I tested it on a few more players that were under donor100 and they did not take damage either. I believe this is a bug since there is no specific hack that makes you untouchable, but if there is I never heard of it.