Conan's Barbarian Levels and Feats for 5e

Barbarian 12 Levels
Howard's Conan stories always center on the contrast between civilization and barbarism, often pointing out the flaws of civility and contrasting them with Conan and his simple barbaric code of honor.

Conan is by and large a barbarian in the 5e sense. Building Conan off of 12 levels of Barbarian gives me a core of abilities that allow the player to "fall back" on Conan's barbaric abilities much in the way Howard would have Conan fall back on in the stories. When it comes to combat, Conan should be very deadly melee class and I have to say the 5e Barbarian captures many of his abilities from the story very well.

HP: 144
Hit Dice: 12d12

The HP and Hit Dice are just for his core Barbarian levels. At level 20, King Conan will also have 5 Rogue and 3 Fighter levels worth of HP and Hit Dice.

Red = Ability Necessary to capture the ultimate feel of Howard's depiction of Conan
Orange = Ability useful in a 5e mechanics
Light Blue = Ability not really necessary to capture Howard's Conan

Class Abilities:
Rage 
Unarmored Defense
Reckless Attack
Danger Sense
Extra Attack
Fast Movement
Feral Instinct
Brutal Critical
Relentless Rage

Path of the Berserker Archtype Abilities
Frenzy
Mindless Rage
Intimidating Presence

There are numerous debates on 3.5, Pathfinder, and 5e builds to capture a true Conan. There seems to be a debate on how to build an 5e Conan, with some multiclassing, some going pure Barbarian, and others going a Fighter build with a splash of Barbarian.

The core of any build, particularly this one, has to be Barbarian to capture Howard's intent with the actual character. Conan reverted to the barbarian when cornered, hurt, or overcoming enormous odds. Any multiclassing build that attempts to capture Conan should have a strong core of Barbarian levels. For 5e, I found 12 levels gives a solid core of Barbaric traits that also allows for key multiclassing to round out the character.

As for class abilities, the Barbarian class captures the core of Howard's Conan perfectly. While I have read some debate on the subject, I cannot see how anyone could read through Howard's stories and not see how a number of these abilities are perfect for building a Conan in 5e.

The essential abilities for capturing Conan's flavor are:

Rage - Conan flies into a Rage when entering combat throughout the Howard stories.
Reckless Attack - Howard puts it best in Phoenix on the Sword:

He was no defensive fighter; even in the teeth of overwhelming odds he always carried the war to his enemies. 

 Danger Sense - Hardly a Howard stories passes when Conan's barbaric senses warn him of danger well in advance of others around him.
Fast Movement - Howard almost always describes Conan's movements in combat as swift. He is often able to move much faster than anyone around him.
Feral Instinct - This ability is also perfectly Conan. He is never caught flat footed, and even when surprised often acts faster than his enemies.
Relentless Rage - This is quintessential Conan. Again Phoenix on the Sword is a great early example:

[Conan] stood like an image of the unconquerable primordial - legs braced far apart, head thrust forward, one hand clutching the wall for support, the other gripping the ax on high, with the great corded muscles standing out in iron ridges, and his features frozen in a death snarl of fury - his eyes blazing terribly through the mist of blood which veiled them. ... They shrank back - the dying tiger could still deal death.

Mindless Rage - I've read several builds that criticize the archtype options for a Conan Barbarian build. Primarily, they seem to think Berserker isn't a great fit for the character. I find this puzzling, because it definitely fits in with Howard's depiction. In particular, this archtype feature is definitely Conan, as we can see in Phoenix on the Sword as an abyssal demon attempts to mesmerize him:

But the horror that paralyzed and destroyed Ascalante roused in the Cimmerian a frenzied fury akin to madness.

 Intimidating Presence - Again, another feature that is pure Conan, although I would extend it beyond one target and possibly make it a single use aura for a duration, as we can see in Phoenix on the Sword:

They stopped short. Conan faced them, not a naked man roused mazed and unarmed out of deep sleep to be butchered like a sheep, but a barbarian wide-awake and at bay ... 

For an instant the tableau held - the four noblemen in the broken door, and the horde of wild hairy faces crowding behind them - all held momentarily at bay, frozen by the sight of the blazing-eyed giant standing sword in hand in the middle of the candle-lighted chamber.

The  remaining abilities are heavily combat mechanics related, so I haven't listed them as "essential" because they relate mostly to the mechanical and not flavorful playing of a Conan character in 5e. Bonus attacks are important to a melee class, as well as the ability for a Conan character to have a high defense without armor.

The Barbarian class with the Berserker archtype is an essential core component of any Conan build. For my purpose, 12 levels gets you all the abilities you would want to play a Conan character in the style of the literary Conan, and still have the freedom to multiclass to round out the literary Conan's abilities.