Fealty is an old-fashioned and somewhat literary word that refers to intense loyalty or fidelity to a person, group, etc. More narrowly, fealty refers to the fidelity of a vassal or feudal tenant to their lord.
Authors who inspire such fealty can guarantee a publisher good sales, no matter the quality of the books they write.
Kneeling before the entire court, the knight pledged his fealty to the king.