Morrigan did so using hypnotism and her draining of sounds through her race as a succubi. Morrigan was incredibly cruel and cold upon capturing, using cunning and lecherous nature to trick her lovers into serving her eternally.
When Rin first took the estate from Morrigan, she was very vicious about about capturing her slaves, exactly like Morrigan was. She used to scope out people she preferred and and those she felt needed to be punished for infractions (such as Yagami cheating on his wife, Nerel. Rin was incredibly predatory and was obsessed with ownership. Eventually, especially after the birth of her two children, Rin became much less possessive, while she still was capturing people she saw as seeing punishment, she was much more caring once they were under her control. The big change happened when she released Morrigan and let her live with Cloud as a normal blind wife. After releasing Morrigan, Rin no longer captures people, instead, she now has admirers who come to her lavish castle above Wimbourne and pledge their loyalty to her. Some do it for money, some do it for food, others do it because they love the Archduchess and her ways. Rin now tries to transfer that motherly love she thrusted upon herself onto her subjects and as of late, many say that their Queen, Mistress Rin Lorei Aensland is perhaps the most gracious of the four regions.