I mean, Hades could play a role in 515’s flashback, which features Hook and Liam. If Liam’s ring (the one that Hook gave to Emma) really does have the power to keep somebody alive, it would make sense if the ring is connected to Hades.
I could see that, especially if Hook and Liam’s brotherly relationship is supposed to juxtapose the relationship between Hades and Zeus.
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"That’s how you know you’ve really got a home. When you leave it, there’s this feeling that you can’t shake. You just miss it." Neal Cassidy