The Order was a guild of lamplighters before the water went out. It is now the only body with a member in every town on the rim, which is a different thing from being a government, though it has stopped saying so.
The lights
Every rim town keeps a light burning towards the basin. The Order says this is for anyone walking back out of the Hollow. Nobody has walked back out of the Hollow in nineteen years.
Oaths
Joining the Order means taking a bond to it in the mechanical sense, and the Order is careful to explain that the tie runs both ways. Members disagree about whether it does.