What is the ruling on adding a third person, who acts as a temporary participant (*muhallil*), to a two-person archery contest involving stakes?

Primary text

If there are two contestants and a third person acts as a *muhallil* (a temporary entrant, often to facilitate a wager), and a fourth outsider then claims to be a partner in the stakes with the actual contestants, this arrangement is void. The basis of receiving stakes or incurring liability is participation in the contest itself.