Need advice on a character concept.

[Abaddons_Bride]

I am trying to make a character that is martial and uses fear to their advantage, but also has access to poison, necrotic and acid spells. I figured that oath of conquest paladin would be my best option for the main theme of the character, because it's pretty much what I wanted. Unfortunately the paladin doesn't have the spells I'm looking for. What would be a decent class to multiclass with to give me what I want?

[Bobthewizard]

A one level dip in sorcerer should get you what you want. Acid splash, poison spray and toll the dead cover your requested damage types. You could take chromatic orb but I'd stick to shield and absorb elements for your sorcerer spells. Magic initiate could get you the shield spell and 2 of the cantrips.

Dragonborn and fallen aasimar have racial fear abilities which tie in well with conquest paladin.

Then look at the sorcerer spell list and decide if you want more levels or not. For conquest, you want to get to 7th for the aura and maybe 9th for the fastest way to combine the aura with the fear spell. Conquest paladin 7/divine soul sorcerer 13 is pretty powerful.

[Evaar]

If Unearthed Arcana is available to you, you might consider the Way of Mercy Monk.

https://dnd.wizards.com/articles/unearthed-arcana/subclasses1

[nickl_2000]

Oath of Conquest Paladin/ Sorcerer Mix would do the trick.

Yaun Ti Pure Oath of Conquest Paladin may do the job too.

[theantesse]

Have you considered a cleric, perhaps of the death variety? Maybe with the feat for a few extra spells? Death Cleric gives you martial weapons, a channel divinity to really pile damage on a good melee hit, necrotic spells, and a bit of poison. Taking a feat for Druid cantrips and 1st level spell could give you a little more poison and acid (at least Poison Spray and Acid Splash if I am remembering correctly) with the same casting stat.