As part of their journey to salvation, they are required to wear the bulky and terribly uncomfortable penance suits. While within these suits, they do not eat, sleep, visit the toilet, or do anything that makes money. All they do is float about, droning idly about the salvation that Zedem offers the faithful. No one - with the exception of the monks themselves - can even stand to be around them. Only the fact that the church gives you an offering of 5,000e makes up for this.
It is said that they wield holy fire that they can use to smite the enemies of Zedem. Unfortunately, the enemies of Zedem do not normally include the intruders, hostile takeovers, and enemy agents you must contend with on your station.
When a temple has twelve monks and has converted twelve penitents, something miraculous happens: the penitents leave. While they do so in a spectacular display of ascending to the heavens in a ball of light, all that matters is that they are GONE. That alone is cause enough to drop to your knees and thank whatever god the church of Zedem tells you exists.
Penitents will also leave via a port on occasion.