ok, what you have to do is:
-get inside arena
-the hard part, server must crash, if you know any way to do that you will be welcome to post it
-after crash, you should have the arena flag and buff (arena preparation), it makes you unattacked by any kind of mobs, and you have infinite mana/energy/rage. You can also give some damage to mob, and he won't attack anyone.
Hope it's not a repost, works on OpenAscent TRUNK r143/Release-Win-X86
the actuall patch is 2.4.1