I have a Great Old One Warlock who is multiclassing into Paladin because his Patron has/is achieving godhood.

The Patron's premise is that they were banished in their attempt to conquer the material plane so they could torment it for all eternity.  In response the Great old One formed a cabal of Warlock who seek to defend the material plane an keep it nice and clean and peaceful until his inevitable return.  For their point  of view, everything in the material plane belongs to the Great Old One and no one is allowed to mesh with their stuff.  No one gets to despoil the innocent but them.

What oath works for this?

I mean...you actually stated "conquer the material plane" in your description. Also, I really enjoy the conquest paladin's play style and abilities. It doesn't have to be played as an overwhelming jerk demanding fealty. You can be a really nice character that is helpful and polite because it allows the future supplicants to open themselves up and drop all their defenses in preparation for your domination and eventual rule. Also, your masters will need generals and lords to rule this rabble when the time of crossing comes and they are powerful enough to return to the material realms, right?

that is a very reasonable argument, I think you are right.  I honestly wasn't expecting someone to come along and make it so simple.  

I have been playing the character for a few months and I think I was focusing to much on his character ark instead of what my lore stated and you've helped me understand that.

Cause he's not a jerk, and he plays a lot like a chaotic good character, cause he does good things and even I got distracted by that and was ignoring if unintentionally that in the end he is lawful evil.  Thank you for the help Chris.  I very much appreciate it.

No problem, I love characters that have a twist in their psychology. LG characters can have trouble understanding what 'a means to an end' really is and have difficulty sacrificing their own sensibilities for the greater "good". LN and CG tend to have a lot more moral ambiguity without undermining personal ethics and any bound strictures. In a sense you could be LG and have the premise that you are defending the people and the land to maintain its perfect beauty for the arrival of your patron. Protecting the weak and destroying those who would undermine the perfection and honor of the realm. You know that the end times will come, that is a certainty, but until then goodness shall reign. It is just the lawful order of things that your duty is to promote goodness in its perfection.

So many twists to have fun with. Heck, you could even think your purpose is to battle your patron upon its return to show proper respect, because you may believe that it might only be able to consume the most pure of hearts.

Yeah, it is a juicy premise 

I've stated him as chaotic good because he doesn't serve the law in any reliable capacity.  It's pure coincidence when he does and he we will absolutely steal, vandalize and revolt if he sees it as producing a good outcome.  He does lots of stuff Lawful Good Character's don't and wouldn't do.

As for the eventual return, I tend to leave it up in the air.  There are any number of very reasonable responses to the situation and I respect any direction a guy takes with that.

I am about to get all high and mighty, maybe even condescending on your views, because I am a jerk that way. Just kidding, but when people try to correct each other with opinion it always reads kind of like a jerk is writing it.

Lawful does not mean you follow the law of the land, it means you follow a stricture or code. Every alignment kind of follows a code of conduct, but they have flexibility in how they interpret the code given certain situations. Lawful alignments will stick to what ever code they have developed with stubborn abandon. With the exception of the Oath of the Crown, I am uncertain if any other paladin follows the law of the land, so to speak. And even that one follows the laws of the aristocracy, which could change depending on who is in charge. I personally think that Oath of the Crown is the easiest to play LE while still being a LG character. You are bound to your Oath not the "law" by being lawfully aligned.

If you think your character would sacrifice itself to uphold its principles in even the most dire of circumstances, you have a lawful character. If the character has a code it wants others to think it goes by, but it really just doesn't give a poop, and changes sides in an argument mid-sentence over and over again depending on how much it personally affects them, probably chaotic. Neutral characters are just 'devil's advocates' in all situations. They tend to weigh things out for the best overall outcome that satisfies their code with some wiggle room.

Good and Evil are usually easy to figure out. Would your character kill an NPC for personal gain?

Another way is the trolly problem. Neutral will hit the lone victim, Evil will hit the multiple victims, and Good will attempt to derail the trolly before hitting the track junction by sacrificing themselves.

yeah but the oath is usually tied to some larger body, or will.  An militant anarchist might have a code that says all government should be destroyed and they follow it to the letter all they want but it won't make them lawful.   Alignment is tied to your effect on the world and what your actions result in.  Lawful actions result in order and i'd say neutral characters are ones that don't consider things beyond their own nose.

You made a mistake in saying evil will hit multiple victims, evil ties them to the tracks.  Neutral wouldn't interfere unless they like the people tied to the tracks.  Good directs the trolley to the smaller death toll and also tries to stop the trolley.  Lawful tries to do the same as good but may not risk derailing the trolley cause the trolley passengers could be hurt.  Chaotic is a crap shoot to decide what gets done based on the character.

Your logic is adding a ton of side bars that are not integral or part of the basic problem. The trolly problem is stated as the person controlling the car has a decision. All other factors are locked in play before the participant is presented. The problem is one of personal morality and personal ethics. And you are correct about the militant anarchist, but by being militant they have chosen to be personally lawful to their code, and by being an anarchist they have chosen to be personally neutral on the actions they exhibit in their encounters until they make up their minds.

Cool discussion, BTW.

The idea of being Lawful because your character follows a code is one thing.  I just don't think the logic holds up when you compare to other alignments.  I don't think you'd so easily claim Count Frollo from Hunchback of Notre Dame is a Lawful Good Character because he believes he is.  His actions result in evil and chaos and I think that's what we consider when we declare his alignment.

I am being an objectivist here, I will admit.  I've never put much stake on personal mortality like your talking about.  The militant anarchist may be lawful to himself, but to the rest of us he is an agent of chaos.  I don't think we can ever distance alignment from a character's actions and I don't think we should.  

I know, it is so hard to try to quantify complex character actions where the weight of repercussion is easy to tilt. I think that is why WotC has kept it around, more for nostalgia instead of mechanical reasons. Even the spells have shied away from this. Detect good and evil is not really that, it is basically a detect magical being of those alignments instead.

And you are right, Count Frollo was LE at the start of the narrative, but at some point he has a conflict of alignment and becomes chaotic evil. Heck, before the actions in Hunchback he may have followed a path more LN and slowly became more corrupt as his power and influence grew. He drifted from his starting alignment through growth and development and ended up a self-serving agent of chaos. I think alignment can still be integral to the GM as a storytelling agent for characters and to warn them when they are about to do something that could be detrimental to their character. If a GM focuses on character backgrounds like dieties, alignment, hell their actual background, the whole gaming experience can change from dungeon crawl to RPing.

Imagine having some great artifact that is bound to a particular alignment and suddenly your GM warns of a character conflict and puts the player in a moral dilemma. Your conquest paladin might suddenly be torn between following their oath or following their alignment or even a god if you follow one. Talk about hitting some rich RP feels.

Also, I just realized this topic has gone way off coarse from its original intent. So many threads are out there on alignment. I just started having a conversation instead of letting your thread breath.

Oh that's fine no one else posted here anyway.  

Re: the topic, The Oath of Ancients also fits.  You would mostly be reflavoring certain abilities so that they are not as Fey-focused.  Instead of Turn Fey and Turn Undead, for instance, you could have Turn Celestial and Turn Fiend.  Whatever type of creature you think your GOO patron would see as the most likely to effectively oppose its conquest of the world.  Instead of Vines popping from the ground for the Channel Divinity ability, make it a writhing tentacle.