In Posse play, the Challenger is the player at the head of a serial chain who is actively in the Duel (plugged to the opposing side’s Challenger).
Each side of a posse-augmented duel has exactly one Challenger per role line.
[Opponent Challenger] ←—— duel cable ——→ [Your Challenger] → Supporter → Supporter → …
Outcomes follow the duel rules for Challengers: winner +1 Quickdraw Points and +1 Energy / Tokens (2027 canon). Supporter contribution to advantage is TBD.