Dead?

Either it’s dead or you will be

It’s dead. If it’s a rear wheel, you likely won’t go over the handlebars and face serious bodily harm. But new wheel day without question.

Yes.

What causes this? I have never had a wheel fail like that.

Thanks for reminding us to inspect our wheels

Would classify it as “dying” or “ticking time bomb.”

You could get a few or more rides out of it but eventually it will fail. The spoke will probably pull through and the wheel will go out of true as a likely scenario. There could be a catastrophic failure (wheel collapsing) but I feel like that’s less likely. My guess is that has been developing for a while and it wasn’t noticed until recently.

Would recommend ordering the necessary replacement parts immediately (rim, spokes, etc. if you want to repair it or whole new wheel).

Continue riding until parts arrive but don’t do any crazy drops. Maybe light XC until it’s fixed.

Are these WTB rims?

Probably overtensioned, that nipple looks pretty beat up.

Dead.