## Blindsight can "see" through the fog

Blindsight allows a creature to "see" through senses other than normal vision. The description reads (PHB 183):

> A monster with blindsight can perceive its surroundings without relying on sight, within a specific radius.

Blindsight [most likely counts as seeing](https://rpg.stackexchange.com/a/191556/63795) for the purposes of a spell that requires sight. There are a couple of ways you can get access to blindsight:

### Magic Items

The **Dagger of Blindsight** is a rare magic item from _Waterdeep: Dungeon of the Mad Mage_ with the following ability (WDMM 86):  
> A creature attuned to it gains blindsight out to a range of 30 feet.

If magic items are available to you, you might ask your DM about obtaining this item. This is the only official magic item I am aware of that provides this sense, but I do not know what may be available in your specific game. You are already outside the realm of official books with the Oath of the Open Sea subclass, so there may be other unofficial options available to you.

### Spellcasting

**_Draconic transformation_** is a 7th-level spell from _Fizban's Treasury of Dragons_ available to druids, sorcerers, or wizards that provides the following benefits (FTD 19):

> With a roar, you draw on the magic of dragons to transform yourself, taking on draconic features. You gain the following benefits until the spell ends:
>
>**Blindsight.** You have blindsight with a range of 30 feet. Within that range, you can effectively see anything that isn't behind total cover, even if you're blinded or in darkness. Moreover, you can see an invisible creature, unless the creature successfully hides from you.
>
>**Breath Weapon.** When you cast this spell, and as a bonus action on subsequent turns for the duration, you can exhale shimmering energy in a 60-foot cone. Each creature in that area must make a Dexterity saving throw, taking 6d8 force damage on a failed save, or half as much damage on a successful one.
>
>**Wings.** Incorporeal wings sprout from your back, giving you a flying speed of 60 feet.

A downside of this method is that it uses concentration, so you would be limited to non-concentration spells if you want to keep the blindsight.

## Wait it out

Another option is just to **wait out the effect** of the fog. 

You state the fog "lasts way longer than any fight", but it doesn't have to. You can use _rope trick_ to hang out in an extradimensional space for the 10 minutes, _etherealness_ to pop into the ethereal plane for the duration, or use _forcecage_ to trap the paladin until the fog effect expires (although with _forcecage_ you have to wait the full hour duration as well, you cannot choose to end it like you can with the other two mentioned spells). You are essentially putting the combat "on hold" until you can fight on your own terms.