The new CW show stars Sarah Michelle Gellar as a woman on the run who assumes the identity of her twin sister.
Speaking at Comic-Con, Charmelo suggested that he will "live and die by [the] twists and turns and secrets" in the series.
"One [of the twin sisters] is driven by redemption, one is driven by revenge," he continued. "You won't know who's the femme fatale and who's the mark. We love delving into the realm of moral ambiguity. There are things we allude to that cause a huge rift between sisters."
Charmelo added: "It all plays into the mythos of that and it's something we'll unravel over the season in flashbacks."
Meanwhile, Snyder suggested that fans will begin to learn more and more about the twins as the season progresses.
"We will give you some answers [each week], we'll leave you on a pop, and when you think you know what's happening, you'll be shocked," she teased.
Elsewhere, Gellar joked that she is really playing five characters in Ringer, saying: "There's Bridget and Siobhan in the present, Bridget and Siobhan in the past, and 'Siobette' [when one twin pretends to be the other]."
Ringer, which features stars including Ioan Gruffudd and Nestor Carbonell, will premiere on The CW on September 13.
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Watch the trailer for Ringer which aired at Comic-Con below: