You're the guy that helps out with everything in general, and you stay objective of Sparksy's decisions, in case he does something wrong. It's like you're a leader, except with less power as Sparksy.
If not, then, I have no idea why there's a co-leader at all. The goal of a co-leader is to either be objective, help out, or replacing the leader temporarily at times.
If not, then, I have no idea why there's a co-leader at all. The goal of a co-leader is to either be objective, help out, or replacing the leader temporarily at times.