So I have a question,

Whats the benefit from playing online? I've been playing offline for a while now and am at level 24 and just noticed that there was an online function. I know that online gives you the reduced bank space, but can't really find anything else that it does.

Can someone give me a quick and dirty about online and those crystal things?

- The offline version doesn't have access to Nightmare or Hell difficulties.
- Character progression is saved locally on the local one - so clearing browser cache for example will erase your character. Server side is saved online so you can jump around if you wish.
- Leaderboards are online-only.

Those are the big points I believe.

That about covers it. Soon-to-come features are all predicated on server account data, too. Chat, profile sharing, item trading, mailboxes, etc.

Is the only way to get those cyrstals is to buy them? Or can you get them ingame somehow? The bank space aint much but I think i'd have fun if i can hit the other difficulties.

Currently there's no way to earn crystals, but that is something that is being mulled. In future patches you may be able to earn them by simply progressing through the game.