A kiss from Lucien can make women never forget him, and the touch of another man will feel horrible, but getting his tattoo is the real confirmation that the woman who receives it will belong to him forever no matter what.
After receiving his tattoo and making that deep soul connection with him, women will always feel that a part of them is missing when away from him, and their life will look more colorful and bright when next to him.
But that is not a one-sided situation. After the 'pact,' Lucien will also feel connected to the women with his tattoo and will not be able to be completely at peace and satisfied without knowing that those women are really fine and happy, which can only happen when they are beside him.