I made this subclass for the Barbarian. It is themed around Bhaal and I'm wondering if the features are balanced so I figured a peer review would help. Sorry about the lack or lore I'll add it when I have it

Subclass (this is the edited version)

Path of the Slayer (Barb)

Level 3: Slaying Fury

If you use Reckless Attack while your Rage is active, you deal extra damage to the first target you hit on your turn with a Strength-based attack. You deal an extra 2d4 plus half your Barbarian level (round down).

Level 3: Slayer’s Body

You have Resistance to Poison damage and advantage on saving throws to end or avoid the Poisoned condition.

Level 6: Slayer Mind

While you are Bloodied you have immunity to the Charmed, and Frightened conditions while your Rage is active. If you’re Charmed, or Frightened when you enter your Rage the condition(s) end even if you are not Bloodied. Additionally, you have advantage on saving throws made to avoid or end the conditions even while you are not raging 

Level 10: Slayer’s Cry

As an Action, you can cause the unholy blood of Bhaal to flow out of others with the cry of a slayer When you do so, each creature of your choice in a 25ft Cone originating from you must make a Wisdom saving throw (DC 8 plus your Strength modifier and Proficiency Bonus). On a failed save, a creature takes a number of D10’s Necrotic damage equal to your Rage damage bonus. On a successful save a creature takes half damage

Once you use this feature, you can’t use it again until you finish a Short or Long Rest unless you expend a use of your Rage (no action required) to restore your use of it.

Level 14: Partial Slayer

You have immunity to Poison damage and the Poisoned Condition. When you activate your Rage, you can assume the form of a partial slayer of Bhaal. This form lasts for 1 minute or until you drop to 0 Hit Points. Once you use this feature, you can’t do so again until you finish a Long Rest.

While in this form, you gain the benefits below.

Slayer’s Arms. Two additional arms grow out from your back. When you make an Unarmed Strike it does 2d8 plus your Strength modifier Slashing damage instead of the normal Unarmed Strike damage. Additionally, you can use them as a second pair of arms but cannot you a weapon with them and can grapple a creature, and pick up or put down a small or tiny object (see the Thri-Kreen Secondary Arms trait for the rules)

Hide of the Slayer. Your gain a plus 2 bonus to you AC

Slayer's Grasp. When you make a melee attack on your turn, your reach for it is 5 feet greater than normal.

Because I can't edit the polls Could you also tell me what about the Subclass needs work? Thanks

Here are my suggestions:

Change the names of the features to all keep them on the same theme: Slayer's XXXXX

Remove the immunity to the Poisoned condition from Slayer's Mind, and move it to the level 3 feature. Maybe tone it down a bit to make it Resistance to Poison Damage and advantage on saves against the Poisoned condition. Then you can grant the immunity at level 14 when the body gets buffed again (maybe immunity to both Poison damage and the condition).

Slayer's cry could use some buffing. A once-per-day ability that lets you deal a small AoE of damage is a little lackluster for a level 14 feature. I would suggest two tweaks. Make it usable once per Short Rest, and let it do half damage on a save.

The level 14 feature is cool, but maybe allow the player to use the Slayer's Arms to make regular Unarmed Strikes as part of the Attack action. Seems odd that their regular attacks might be doing less than their bonus action attacks. Maybe word it as "While in this form, you can make Unarmed Strikes that deal 2d8 + your strength modifier slashing damage, and you gain the ability to make one Unarmed Strike as a bonus action."

Overall, I love the themes and the progression of turning more and more into a slayer as you get higher in levels. This is a subclass I would be willing to play in game.

So, Sequilonis I took what you said and edited it. It is at the top of this post under subclass.