I think the reason he wanted the baby was because he knew she’d never fulfill her deal. I think he was crafty enough to know Charming would imprison him. He needed the name of their baby and knew they’d come to him in the cell. He knew Regina was enacting the curse so he played the Charmings for the name of their baby and Regina for wealth and comfort in their new home. I don’t think he ever really wanted the baby, but wasn’t above taking it if she did give in to the deal.
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Keeper of Rumplestiltskin's and Neal's spears and war paint and crystal ball.