So last night was our first session of the new year and players were heading to the next part of the campaign. Well they decide to camp on the first night and usually during nights I have three watches. The first watch nothing happened. The second watch, two of my players got alittle bit of a scare as I had a minor illusion of a shadowy figure appear in front of them with glowing red eyes. After awhile a the figure vanished. The final watch came up and these two players were scared shitless as I had a them roll a wis save from a cause fear spell. They both failed. As they were heading back to camp, a darkness spell activated, so they couldn't see a thing. I had them both roll another wis save. One player succeeded the other failed. Our Paladin who was no longer scared tried to call out to the ranger. Which caused a deafness spell to go off so the ranger couldn't hear him. To finish off this scare tactic I had the dancing light spell casted and began to circle the ranger. 

At this time, the rest of the party got to them and dispelled the darkness spell. 

Now at the table, I always bring a bluetooth speaker with and had some spooky music and ambient sounds playing to really help with this. 

Now with this being said I now have an idea of a dnd character that loves to use fear tactics. I was thinking Fallen Aasimar and of course go with some spellcaster level. Any suggestions on the spells they should know

Illusion spells like silent image, major image, and hallucinatory terrain can work well for this. Dream can be both a plot point and a fear tactic. Spells like black tentacles and shadow of moil can be described in similarly eerie ways. Oh, and of course maddening darkness is amazing for this, even though it's super high level.