Board Thread:Spoilers!/@comment-27060727-20160808004056/@comment-28473728-20161013215319

i think they are unkillable because they are stilll a part of living things (regina, jerkyll), just a separation

so unless the regina or jekyll is killed their serum counterpart remain undead

something tells me that jerkyll backstory will somewhat reflect rumple past that there is a girl who loves the man inside the monster, with the only difference is that there is no happy ending for Hyde (he will kill Mary somehow i guess)