My plan is to mix the Champion's Improved Critical Hit class feature with the Great Old One's Mortal Reminder class feature. Crits on 19-20 that force an AoE WIS saving throw vs. Frightened. In my head I feel like this could work unarmored with invocations, a 1 level Barbarian dip for CON AC, and robes you find later in the game that give 2 CON (effectively 1AC for Barb).

Starting stats can be:

STR 10

DEX 13 1 (14 total, 2 Initiative & 2 AC)

CON 15 ASI[1] (16 total, 3 CON bonus to hp & unarmored AC)

INT 8

WIS 10

CHA 15 2 ASI[1] (18 total, 4 bonus to Pact-Weapon Attack Rolls, Damage, & Spell DC)

Total Unarmored AC: 10 3(Mage Armor) 2(DEX) 3(CON from Barb1) 1(Dual Wielder) = 19AC; I'm not sure if lowering CON, raising DEX, and using Light Armor is better though.

The plan is to take 6 Levels of Champion to give us:

1. All equipment proficiencies, STR & CON proficiencies, TWF Fighting Style

2. Action Surge

3. Improved Critical Hit

4. Feat (Dual Wielder?, ASI [ 1CON, 1CHA], ???)

5. Extra Attack

6. Bonus Feat (Dual Wielder?, ASI [ 1CON, 1CHA], ???)

We'll add to that 5 Levels of GOO to give us:

1. Mortal Reminder, EB I guess?, Dissonant Whispers for ranged Frighten attempt?

2. 2 Invocations. Not sure which ones would be most ideal. Armor of Shadows if going the Barb1 unarmored route but otherwise Devil's Sight and...?

3. Pact of the Blade for eventual extra-attack stacking possible-bug abuse, plus making your main weapon use CHA instead of STR/DEX allowing us to condense our stats. Also some useful spells like Darkness, Mirror Image, Misty Step, Hold Person.

4. Feat (Dual Wielder?, ASI [ 1CON, 1CHA], ???)

5. 1 Invocation, Extra Attack, 2nd EB beam, useful spells like Counterspell, Fear, Hunger of Hadar, Hypnotic Pattern (assuming ground DC bug is fixed)

And that's what I've got so far.

That's 11 useful levels in total. Champion7 could give us Remarkable Athlete which I don't think is one of our most useful choices. Warlock6 could give us Entropic Ward which (if I'm reading right) is once per long rest? Pass.

So 1 level dips, which are the most beneficial for us? Some ideas:

Barbarian1 for CON Unarmored Bonus, as I mentioned at the top. Rage could be situational with it's Resistance but only twice per long rest and conflicts with our ability to have handy spells at our disposal.

Light Cleric1 for Warding Flare seems like a good defensive reaction dip.

War Cleric1 for War Priest. 3 Bonus Action Attacks per long rest. So 3 times per long rest we can Attack, Attack, Attack, Action Surge, Attack, Attack, Attack, War Priest Attack. Is that correct? Sounds great but is it actually useful only 3 times per long rest?

As for gear, I try not to be too gear dependent especially as a lot of good things come 70 hours into the game but obviously the Shortsword with crits on 19 (18 when stacked with Champion) is probably a must. I don't know if any 2Handed weapons have that benefit but if they do we could replace Dual Wielding with GWF/GWM instead. Also a couple of pieces to boost our Spell DC to make it harder for enemies to resist Fear, Hold, etc.