What is a beta?

What would i exactly do if i join the Dark Avatar Beta

Basically, play the game as thoroughly as you can and report any crashes, bugs, errors, mistakes, or oddities you come across.

and is there a cutoff time to when you could join the beta

I'm not sure, but it is open now so if you hurry you can be sure to get in.

The word on the street was that new additions would be allowed to play each 'milestone\release' of the beta. However, as it currently stands (and this is subject to change) it is an open-pre-order beta. You buy it, you get to help play test it. Sometimes it can be frustrating, but it is also really nice to be able to help make the game, with suggestions, tweaks, additions, etc.

If you are willing to really get down n dirty playing a game, it can be very rewarding. If you aren't one to put up with errors n such, avoid. You will have various crashes and bugs with each release, though there should be fewer and fewer as time goes.

Now, this is not to scare you off, but please don't pre-order, play the beta, only to be surprised if you get a crash (played 5 games and only had crashes in 2 of them). All in all, I think it is a great deal of fun to play and help make this an amazing expansion.

Thank you.