Essence Thief

The Essence thief believes that even if they aren't the best, they can just take the traits that make someone else the best instead. They drain some of the essence of individuals they touch with their magic, taking on their physical traits as they glide across the battlefield, accumulating power.

Essence Theft

Beginning at 3rd level, you gain the ability to steal some of your victims' essence with but a touch. You can steal essence from a hostile creature using a Dexterity (Sleight of Hand) check opposed by their Strength (Athletics) check or Dexterity (Acrobatics) check, or as a result of dealing sneak attack damage to them. You can also steal essence from a non-hostile creature using a Dexterity (Sleight of Hand) check opposed by their Wisdom (Perception) check.

On a success, choose two Attributes. For the next minute, ability checks using those attributes have advantage, and the target has disadvantage on ability checks using those same attributes. These stolen attributes might manifest on your body as simple glowing marks, or they might manifest as suddenly appearing muscle, sexual characteristic mass, body fat, height, or other traits which do not count against your character's total weight or other characteristics. After the minute is over, these attributes recede as they are expended.

This ability's duration increases to an hour at 17th level.

This ability can be used a number of times equal to your Charisma modifier (minimum 1.) You regain all expended uses of this ability after a long rest.

Essence Devour

Also at 3rd level, the rogue can choose to drain some of the essence from a creature they kill and make it their own. Unlike Essence Theft, this drain is permanent. Whenever the rogue kills a creature, they can choose to gain weight (fat or muscle) or height (Which cannot increase their size category) in any combination from the creature, up to a number of pounds of fat or inches of height equal to 1d10 + your Charisma bonus + your Rogue level, distributing across their body as they like, with every one point being worth a pound of mass and every 5 points being worth an inch of height. This essence does not have as much flashy potential, but has a practical application: The rogue can expend body mass or height to fuel temporary proficiency with the skills and tools they are not currently proficient with.

At the cost of 10 pounds of mass or 2 inches of height in any combination, the rogue can use this ability before making a roll to gain proficiency in any skill they do not currently have proficiency with for one skill check, or with a tool, vehicle, weapon, or armor they do not currently have proficiency with for up to an hour.

You may use this portion of this ability a number of times equal to your Charisma modifier (minimum 1.) You regain all expended uses of this ability after a long rest.

Improved Devour

At 9th level, you have improved your ability to convert essence into skill on a temporary basis. You can expend one use of your Essence Devour ability to gain expertise on a skill you already have proficiency in for a single check, or with a tool you already have proficiency in for up to an hour.

In addition, you can expend two uses of Essence Devour to do the same for a skill or tool you don't currently have proficiency in.

Thief of Faces

At 13th level, when you use your Essence Theft ability on a humanoid, you can choose to take on the appearance of that humanoid as well, turning yourself into perfect visual copy of your victim. You retain your physical and mental stats, but take on their appearance, height, and weight for the duration.

Additionally, while you've stolen someone's essence, you can attempt to extract information from them by using your action or bonus action to force them to make an Intelligence Saving throw. The DC is 8 + Proficiency bonus + your Charisma modifier, and on a failure you learn the truthful answer to one question of your choice. Once they succeed on the saving throw, this portion of this ability cannot be used on them again for the remainder of the duration of Essence Theft.

Essence Assassin

At 17th level, your ability to steal essence has improved, and the drain has become so potent that it leaves enemies winded. A creature who you successfully use Essence Theft on gains the Poisoned condition until the ability's duration ends. Additionally, they are always a viable target for your Sneak Attack ability, even if you have disadvantage on your attack rolls against them.

If you kill a target under the effects of Essence Theft and use Essence Devour on them, the effect of Essence Theft remains until the end of your next long rest.