I'm currently running a homebrew game in a setting of my own world and I've run into a bit of a quandary regarding how to handle one of the less well defined aspects to the paladin class. Just to aid in the context, here's a little background before I get to my question; the setting is a world where the pantheons from the Forgotten Realms have long been outlawed as false pagan gods, and most part have largely been lost to time. There is a monotheistic religious order which dominates the cultural landscape, and has positioned itself as the voice of morally and law in society.

Now, one of my players is a paladin who belongs to this order, a fact which none of the other players are aware of in any meaningful specifics (yet). In the background for his character he was approached by a council of bishops to halt his training to become a crusader, and was tasked with a mission to go back out into the city and befriend a man (another player) suspected of being a druid, in the aim of uncovering the identities of leaders running the illegal pagan network. Long story short, he started the adventure as something of an unconventional spy, more than a little uncomfortable with the subterfuge. We started our first game with him having successfully befriend his mark (who still has no idea 18 sessions into our campaign that the paladin player has a secret agenda).

Here is the where I'm at a bit of a loss at what to do: the nature of our game involves the players getting into a lot of scrapes with the unjust and oppressive laws of the setting, and in the last session they all successfully staged a prison break to rescue an NPC. While in the prison chapter (and building up throughout the game) they've all had their morals and values challenged, and they've all had to take some drastic actions in order to survive. I've really enjoy throwing difficult moral issues at them and watching them struggle with it, but I've come to realise that the paladin player has almost certainly broken a handful of his oaths at this stage. 

He's taken an 'Oath of Devotion', which has the following tenets: Honesty, courage, compassion, honor, and duty.

For 'honesty' he walks the line of not telling any lies (unless you count lies of omission), and the other character seems to have taken a genuine fondness for him, so he hasn't really been grilled by anyone on where he stands on his faith. 'Compassion' his character has shown to many of the down-and-out NPCs they've encounters along the way, which works too, but he has also fought alongside the party with the intent to kill when encountering hostile members of his own order (who were unaware he was 'undercover').

The problematic one is 'duty', where his loyalties are being heavily tested. The prison they had staged the break from was run by his religious order, and inside he witnessed the horrific and inhumane treatment of the prisoners interred within, which has left him questioning his place in the church. If he decides that he has been mislead and that he wishes to leave the order then how would I as the DM handle that? "Oathbreaker" doesn't really feel right, as his actions and motivations are still decidedly 'good', even if he goes along with the more chaotic aspects of 'good' to maintain his cover. I was thinking of telling him that if he wants to leave the order, he might need to change his class to fighter, but I'd rather not since he seems to enjoy the paladin.

What's the deity of the monotheistic religion like? Is it possible that the Paladin could interpret that the religious order in power is violating the tenets of the deity, and therefore see his duty as opposing them? There are certainly real-world analogs to this -- pick any religion you want that has more than 5 worshippers in it, and you will find at least one who thinks that the rest of them are "violating the true faith" and oppose it. This has led to many wars -- fights for which interpretation of the religion is correct. 

This would depend, though, on the viable interpretation that, let's say, the monotheistic deity is "good and kind" and the order is being cruel and violating the intents of the deity, misinterpreting scripture, etc. In other words, the Paladin comes in and turns over the tables of the money changers... that kind of thing.

The 'deity' is more of a lionized messianic figure. I don't want to make any real world analogies since.. yeah not touching that with a ten-foot pole.

But I would absolutely say that the ideals of the deity has certainly been corrupted by those in the church who thirst for more control and power. I've written loads of little prayers and parables for the players from this religion, and it's all stuff like "The messiah gave salvation and mercy to the greedy by smiting the wickedness from them with his hammer'. So you know.. they have a very warped idea on what mercy might look like. I'd say my idea of what the personality of the 'original' deity might have been like is something more like 'lawful neutral', than anything 'good'. It's all an emphasis on order, and judgement.

(I heavily stole from the Thief games, and their 'Hammerite' religion)

GIven what you said I'd be inclined ot say he is largely upholding his oath but it would be possible to reswear his oath to the "pagan" network now that he has seen first hand the treatment of those captured by his church. You could give him the option to speak candidly to the other characters and say this is/was the reason they joined you folks but based on their adventures/work they have come to see their previous life was not what they thought it was. You could have the druid preside over a new oath swarring, maybe let the paladin change to Oath of Ancients for a more Druidic feel, Oathbreaker is quite Evil in intent which this paladin does not seem to be.Make it into a big roleplay moment.

If you wanted some rammifications you could then have a curse of sorts where a mystical mark appears on the palaidns forehead that clerics and paladins of his former faith can see through use of their channel divinty powers or that appears whenever a divintation spell (cast by anyone) is used near him that effectively brands him an oathbreaker of the faith. That way his former associates may eventually realise he has joined the opposition but it is not an immediate death sentence should he need to go back home so to speak. If you went with the divination spell option to reveal the mark then the druid or any other spell caster in the party can get the reveal and put plans in place to try and remove or hide it (Nystul's magical aura would be the easiest way to hide it, Nondetection spells a close second and an Amulet of Proof against Detection and Location a third).

I would work with the player to manifest this through story - maybe find one of the outlaw gods for him to become a paladin of and have him potentially struggle with his powers maybe spend a session without being able to use class abilities and have it be a story beat.

the important part of this is working with the player. Rather than making the decision and forcing them that way.

Quote from syzygyeolith >>

 

But I would absolutely say that the ideals of the deity has certainly been corrupted by those in the church who thirst for more control and power.

 Well that doesn't sound familiar at all ;)

If that is the case, the Paladin should have no problem. If his actions align with those of the god, he isn't in any trouble even if those actions aren't the same as the corrupt clergy.

There’s always the option that the paladin doesn’t get his power from the god at all. I know this concept can start a controversial thread all its own, and I’m not trying to get into whether or not, by RAW, it’s allowed. But it could be that it’s what happens at your table. Maybe your pally gets his power from his oaths. 
Or maybe he’s getting them from a god, just not the one he thinks. That even though he’s sworn to the church, a different, previously unknown god is, kind of, intercepting the pally’s devotion and granting his powers.

Ahh, plenty of great ideas, and different interpretations of how paladins powers might work! That's exactly what I was looking for, thanks everyone.

I'm looking forward to getting on discord to work it out with him, away from the table, and helping him set up some more exciting plot reveals. :)