His shadow became trapped in Omble while tracking a fugitive. If the player talks to his shadow during the Shadow Quest, Silence can be recruited once the player completes the quest in any scenario except Fuse's, T260G, and Riki. In Fuse's scenario, the player can recruit him right outside of Omble without needing to enter, the latter 2 cannot get him due to the lead character needing to interact with his shadow inside Omble.
Silence is mute.
In Essence of SaGa Frontier, Fuse reveals that he has fought alongside Silence in IRPO. Fuse is, by his own admission, quite talkative, so he finds Silence's mutism annoying.
Mesarthim can not be recruited if Silence was already recruited.
Although Silence is related to the Shadow Quest, he doesn't have the Gift for Shadow Magic and cannot get it as well.