The expression "hold in thrall" means to captivate or fascinate someone. There are several synonyms that can be used to express this concept, including spellbind, mesmerize, entrance, enchant, bewitch, fascinate, and enrapture. These words express the idea of being under another's influence or control, of being absorbed by something or someone in a way that cannot be easily shaken off. To hold someone in thrall is to exert a powerful pull on them, to captivate them so completely that they are unable to break away. Whether we think of the pull of a great work of art, a mesmerizing performance, or a charismatic individual, there are many ways to describe the emotional hold that such things can exert on us.