[quote=@WiseDragonGirl]
Can one join as many or as few of these challenges as they want?

Because
<Snipped quote by Terminal>

I've already done that, kill off a main character or favourite character. I often have a main story and then several stand-alone side stories/alternate universe stories and people have died in such side stories. So my biggest problem isn't the task itself, but inspiration for a new story with one of my favourite characters in which that happens >_< I've been going over options, but nothing decent so far.

[/quote]

You can join as many or as few of these challenges as you would like. I can tell you there definitely will be at least one challenge in the future that will make you have to do something you've never done before.

Also, just as a general comment not directed at anyone: There may be an ulterior reason to participate in all twelve labours.