The Rangers of Trinity is a very old guild, the leader and creator was a DM on ROT I forget his name though but he no longer plays.
At one time before I made the Honor Guard guild I was a officer in that guild. I still have one character that has access to the guild hall and that wares the cloak of the Rangers of Trinity.
As far as I know I think the guild is pretty much inactive now. If anyone is still around from that guild hopefully they can speak up. From my memory you just needed to be good alignment to join and swear to protect Trinity.