> The phrase is 'betting your life'.
I have mentioned such a phrase a couple of times, so maybe I know it. The problem is the punishment in question is not as simple as death, where an obvious antonym of 'life' could be used.

>>>14322
These lines sound like they would only make sense after the conditions of the bet were already established, and what I'm looking for is a way to establish them.

Okay, maybe I'm too focused on trying to fit it all in one sentence. But maybe a better direction would be not to combine the two sentences, but to distance them even more, so that the first sentence says they could bet, which sounds like just an expression without actual stakes, and then the second sentence says they would actually accepted such a bet even if the conditions included the punishment. So like this:

... they could have bet that [lots of text here]. And it wasn't just an expression: they were so confident they would have actually accepted such a bet even if the punishment for losing was [punishment].

That should work, I think?