I just remembered, this was mentioned in that TV Guide article, in relation to Chernabog:
Regina, who has reclaimed her job as mayor, and Emma (Jennifer Morrison) will inadvertently release a prominent creature from Disney lore. But, unlike the snow beast from Frozen that terrorized Storybrooke last fall, executive producer Adam Horowitz says, “this monster is not just about wanton destruction. It will lead to a startling revelation about Emma — something that’ll be huge news to the audience.”
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