Spend the vis when you roll. Said vis ads to botch dice. Any other way of looking at it is to prevaricate the intent and twisting in the wind like a shifty lawyer trying to sue because the coffee was too hot.
I'm going to go a little off topic here. I don't think Vis should be allowed in certamen at all. I know it's a hoary old Ars Magica tradition, going back all the way to 1st edition, but it's never made sense to me.
Certamen is supposed to be magical dueling, an alternative mechanism of dispute resolution to out-and-out magical violence. In any historical dueling tradition that I am aware of, the participants were granted equivalent weaponry. To pit a fully armed and armored warrior against a naked opponent armed only with a dagger would be murder, not a duel. The same goes for two magical opponents, one loaded with vis and the other not. I don't see why the Order would ever accept such a way of dueling as a binding form of arbitration.
Hi,
Me:
You can use vis during a Certamen to add +2/pawn to any Attack or Defense roll you make. The vis is declared and expended using the usual rules, ie before the die is rolled.
"At any time during a Certamen" does not allow you to add +2/pawn to your opponent's rolls when he has just rolled a 0 and is about to roll botch dice. It does not allow you to add to your attack roll after your opponent has defended. It does not allow each contestant to bid up their rolls with vis after both the attack and defense rolls have occurred. It does not allow you to break any other rule. It allows you to modify one or more rolls of the appropriate kind, in the appropriate way, regardless of which other rolls you did or did not modify.
Anyway,
Ken
First of all, thanks to everyone contributing to the discussion!
Second, all the folks who say "the very last moment is just before you roll" - do they mean that the defender can choose the amount of vis based on the choices/roll of the attacker? Or do you assume that the choices are made "blindly" and thus effectively simultaneously at the beginning of the half-round exchange?
We roll simultaneously. There's no indication that there should be a delays IIRC.
Well, "equivalent" is a rather vague term. Two knights battling each other, even in a very formalised situation like a tourney, often had weapons and steeds of widely different quality. To me allowing vis seems equivalent to allowing weapons. If you are poor and can afford to spend only two pawns while your adversary can afford to spend two rooks ... well, in that aspect of "magical puissance" he clearly outclasses you, and would definitely have a large advantage on the battlefield of a Wizard's War.
Without mind reading, it is difficult or impossible to know how much vis the opponet is throwing down. The player may know because of the structure of a dice roling game. But to act on that knowledge is metagame munchkinism.
However, if the character did have some inside information (illegal InMe) and had initiative, then maybe.
Hi,
I wouldn't worry about it. So what if the player knows and acts upon it. Probably the player will kind of act on it anyway, even if he thinks he isn't. Certainly the GM will act upon it, because GMs do that even when they think they don't.
Life is simpler not to worry about it. And there's not much to worry about anyway; it isn't like knowing what happened during scenes a character wasn't present for.
Anyway,
Ken
That is ... unclear at best. It really depends on how you represent certamen.
The 3rd edition certamen example, for instance, suggested that you did have an idea that the opponent was drawing on "extra power" and a rough idea of how much that was.
I do myself prefer, however, a certamen where everything is declared at the beginning of the current "half-round" at the latest (with the exception of some certamen style options).