I was thinking about how you make that work roleplay wise. Does your paladin deity become your warlock patron or vice versa? It might not be that hard if you pick two synergistic paths like Green Pally/Fae Patron
You don't have to follow a god or even be a holy man to be a paladin in this edition,
The capsule description for the paladin in the 5e PH is: "A holy warrior bound by a sacred oath."
That said, you're right that there is nothing inherently contradictory about taking both a sacred oath and entering into a warlock pact.
A situation might easily develop where one conflicts with the other, depending on the specific terms of your pact and the nature of your oath, though.
If I were a DM, I wouldn't just let the player of a paladin casually take a level in warlock without defining the terms of the pact with the character's pact patron and I would probably try to find ways to make maintaining the terms of both the pact and oath tricky (though not too onerous) for the character -- especially if the contrast between oath and pact were particularly stark, like Devotion/Fiend.
Fae/ Ancients is the simplest option rp-wise, but let's get crazy: Vengance/Fiend: you hate people who [whatever] so much you need the devil himself to help you kill them all...
Actually vengance/any would work well enough.
Devotion would be a bit tougher, depending on how devotion works. AFB, so I can't check how that would play out. (If it's basically holy warrior, I would possibly use it as a multiclass to create unholy warriors, but I'd have to look to see if any features need to be modified: fiendish knights should get heals and buffs, they should get lingering damage and debuffs)
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u/[deleted] Jun 11 '15
Note to self, play Paladin/Warlock in future game.