The few demon hunters who take the mark of souls are the illidari's greatest interrogators. Using their weaponry to reap the souls of their foes, they implement vicious techniques to learn everything they can about those who oppose them.

Bonus Proficiency

Starting when you choose this mark at 3rd level, you gain proficiency in the Insight skill if you don't already have it. Your proficiency bonus is doubled for any ability check you make that uses this proficiency.

Extract Soul

Also at 3rd level, you can strike the soul of the enemy to extract crucial information about your foe. Whenever you hit a creature with one of the attacks granted by your Demon Bite, you can learn the following attributes about the target: Damage Vulnerabilities, Damage Resistances, Damage Immunities, and Condition Immunities.

Illidari Interrogation

At 6th level, you can pierce a creature's soul with precision, temporarily causing them to be unable to mask their true thoughts and intent. If you manage to hit a single creature with two or more attacks in one round, you can spend 1 fel point to force them to make a Charisma saving throw. You can choose to have these attacks deal no damage. On a failed save, the creature is unable to speak a deliberate lie for 1 minute and all Charisma checks directed at the creature are made with advantage for the duration. You know if they succeeded or failed on their saving throw.

An affected creature is aware of the effect and can thus avoid answering questions to which it would normally respond with a lie. Such a creature can be evasive in its answers as long as the effect lasts.

Soul Rending

Also at 6th level, when you use your Extract Soul feature, you gain a number of temporary hit points equal to 2d8 + your Intelligence modifier.

You can do this a number of times equal to your proficiency bonus, and regain expended uses after a short or long rest.

Illidari Inquisiton

Upon reaching 10th level, your metamorphosis greatly enhances your ability to interrogate your enemies. When you use your Illidari Interrogation feature, you can spend 2 additional fel points to give the target vulnerability to a damage type of your choice for 1 minute, or until they take damage of that type.

Soul Shatter

At 17th level, whenever you hit a creature with one of the attacks granted by your Demon Bite while in your metamorphosis, you can splinter their soul. The creature must make a Charisma saving throw, taking 8d6 necrotic damage on a failure or half as much on a success. Additionally, up to three additional creatures of your choice within 30 feet of your original target are struck by soul shrapnel and must make a Charisma saving throw, taking 4d6 necrotic on a failure or half as much on a success.

Once you use this feature, you can't use it again until you finish a short or long rest.