I don't frequent the WizKids forums as much as I did, and rather than search through dozens of posts, I'd like to see if anyone has seen a ruling on this.

The rules state:
What does this mean?

1) Underdog: I'm spending an underdog token.
Opponent: OK, I'm going to reroll this die.

2) Underdog: Reroll 2 dice.
Opponent: I'll reroll these two.

3) Underdog: Reroll those two dice.

It was ruled over at wizkids that it is once per attack. Think of it like Scott Graves's P.A.

I'm confused,so during the widowmaker solaris fight, your opponet can force you to reroll every round if they have a lower weight total?

Basically.

As long as they still have tokens, they can do it once per turn. If I'm understanding it correctly.

That's not the issue. I understand that one (you can't keep forcing rerolls of the same attack by spending multiple tokens).

The issue is the "reroll any number of dice." Who gets to choose the number of dice rerolled? If less than 3 dice are chosen, who choses which of the dice in the attack roll get rerolled?

I think the underdog player choose the dice to be re-rolled or choose which of your dice he wants you to re-roll. Good question and I could be wrong ... but this has yet to come up on the WizKids forum ... so maybe you should go ask there, and then it official.

Yeah, I went there and was getting an error message trying to get in. Maybe tomorrow.

I think it would only make sense if the underdog got to pick how many and which dice to re-roll, but thats just my opinion.

Yeah, that's the official answer.