About the wither...

[naithantu]

"randomly die" = you failed and the wither killed you. If you die, then you can lose items. Survive harder!

Also, this is still being worked on. The plugin part is done (and has been done for weeks), but worldguard is a bitch and I still haven't figured out why it won't let the wither spawn >_>

[naithantu]

Great news! Lobster figured out why the wither wouldn't spawn (it took him 1 second. I wasted so much time looking at the wrong plugin ._.').

This means... the wither arena is done!
There is a tp pad to the arena located under the nether portal at spawn.

You can build the wither on the 3 lamps in the middle of the arena, the player that built it (placed the middle skeleton skull) will receive the nether star when the wither is killed.
If the player that built it is dead or offline when the wither is killed, the star will just drop on the floor.

[veryunderstated]

If you created the wither you have to be present in the arena when the wither dies for the star to be put in your inventory, right?