To persuade means to convince someone of doing something. In Evony, players can persuade enemy heroes to join their side by bribing them with medals. This can happen when a player captures a hero through various ways. The player can then give the hero medals in order to persuade the hero to join their side. It is only recommended to persuade heroes if they have quite good base statistics, and maybe even better then a hero that you have. In this case, you can replace your hero with the captured hero. It is important to judge well, as a level 10 hero may have the same stat as a level 30 hero. In this case, the level 10 hero is a lot better, as it's stats can be upgraded further than the hero that is at level 30 already.