Summa Servus

Summa Servus - the spell magical binds a person to the caster forever. They will be magical compelled to follow all orders and tasks given by the caster. Their mind will be molded to accept their fate and want to serve the caster for life.

Harry wondering if this is even possible studies the incantation and wand movement. Once he believes that he has the spell down who does he try the spell out on?