Certamen with more than one opponent?

I have a silly story scene / concept in my head:

A stranger (a Hermetic magus) introduces himself to a gathered group of Hermetic magi as 'recognized as an Archmagus in (elsewhere, far away, & strange) location'. Knowing the Archmagi of the local area are going to object to his use of that title, he proposes a very low-stakes ('for love') round of Certamen as his bona fides. The ritual he performs looks quite a lot like Certamen; and he looks around the chamber, in turn selecting three of the Archmagi present to name their preferred TeFo. As they announce their choices, he extends the Certamen arena to them; once they are all in, they begin.

I have not seen anything (and maybe it is just me not being perceptive enough) in the RAW which explicitly states that Certamen is a duel between exactly two magi -- although that does seem to be heavily implied. In HoH:TL the description of 'Gladiatrix' style implies that team-vs-team Certamen has not been developed.

There are also no official mechanics for a person to make more than one attack in a round, although it is spelled out that a person always gets a defense vs every attack. Multi-casting is allowed; but usually is discussed as a function of Spell Mastery -- and there are no spells (except vs an unconscious loser) in Certamen. The rules for 'Concentration' on page 82 say that a magus must concentrate in order to cast a spell; if distracted they must make a Stamina + Concentration + Stress Die roll vs an ease factor -- and the table on the same page lists 'Casting another Spell' as an Ease Factor of 15, which implies casting two spells in a round (even without Mastery) may be possible. Does this also imply more than one Certamen attacks are possible in a round, with an obviously difficult Concentration Ease Factor?

Would one person challenging several opponents at once like this require a breakthrough, or is it something possible-but-not-done? Is it reasonable to allow this, but impose a Concentration penalty for facing additional opponents? How much would that penalty be? Would that Concentration penalty be appropriate (or reduced) if the challenger was restricted to only a single attack per round? Is there any way to reduce the chance of botching in Certamen, since Spell Mastery, Careful Sorcerer, and Cautious with Ability (Certamen) seem to not apply?

I just stumbled across a whole hornet's nest of questions, and thought I would ask the folks here.

Yes, challenging several opponents at once would be breakthrough material. Certamen is a duel.

Corebook pg. 89 (emphasis mine):

Certamen (“Care-TAH-men,” Latin for “duel”) is the ceremony by which two magi conduct a magical duel.

As written the rules seem to assume two magi (and explicitly mention two magi in several places). But there doesn't seem to exist a formal prohibition against multiple magi, or a reason for which only two magi can engage in certamen at a time. And since magi in certamen act according to their initiative it surely seems like we could have several magi engaged in certamen, at least theoretically. It is explicitly stated that certamen can happen in the midst of a combat.

As for rules, personally I'd just make it akin to combat. You can have each magi acting separately or, if they have prior training, a trained group certamen --- as long as all magi in a group choose the same arts and have their arts within a reasonable range the leading duelist gains a bonus to his attack and defense totals (3 for each extra magi, to the limit of the leading duelist leadership, seems ok to me). The "same arts" and "reasonable range" requirements are enough, IMO, for trained group certamen to be unusual.

I like the idea of developing group certamen as part of Original Research. One possible font of inspiration could be the wizard's vigil spell.

I am looking at p89 of the main rules, under the "Certamen" column


and things like the "aggressor" traditionally chooses Technique and Defender chooses Form.

The very first sentence explicitly states "two magi", and everything else implies two magi only.

Something that canonically can be participated in by multiple magi is the (originally) apprentices' game, Bellum (pg 57 of Apprentices). That's mostly a finesse contest (at least if played straight).