Essence Devourer the Ever Changing

The Essence Devourer does not merely grant magical potency to their charges, but gives them the means to acquire their own strength. As energy flows upwards along the food chain, so does all things to the devourer. All eventually rests within the devourer, its aspects changing according to the shifts in consumed universes within. Instead of gaining additional spells known, they gain the ability to absorb the supernatural abilities of enemies they encounter.

Absorb by Experience

At 1st Level gain the following ability.

When you are targeted by or included in the targets of special ability of an enemy, such as a frightening roar or a dragon's breath attack, you may use your reaction and expend a spell slot to absorb that ability. You are automatically hit by the ability and all of the effects, but gain the use of that ability. To learn the ability, you must not be rendered incapacitated or unconscious by the effects. The ability uses the description from the creature's text and your attributes to determine its effects, saves, and damage. The ability must be a natural ability inherent to the creature using it. If the ability does damage, it is limited in the number of dice it may deal to half of your Warlock level rounded down. Abilities use your Spellcasting attack and saves, but are not spells.

You can remember up to 2 abilities in this fashion. If you would learn an additional ability beyond what you can remember, you must forget and lose access to an ability you already know.

You can use your abilities a number of times equal to 1/2 your proficiency bonus rounded down. After a long rest, you regain all uses of your abilities.

At 5th, 9th, 13th, and 17th levels increase the number of abilities you can remember by 2.

Essence in the Flesh

At 6th level gain the following ability.

Spend an Action to consume a small portion of the flesh a creature that died less than one minute ago. Gain 1d8 temporary HP and heal the creature's Constitution Modifier in HP.

If the creature you consume targeted you with an ability that qualifies for Absorb by Experience since your last long rest, you may expend a spell slot to learn that ability as in Absorb by Experience.

You can use this feature as many times as your Proficiency Bonus. You regain all uses of this feature when you take a short or long rest.

Flexibility of Form

At 10th level gain the following ability.

When you use Essence in the Flesh you can now absorb physical characteristics and abilities that you would not be able to absorb according to rules in Absorb by Experience. When you use Essence in the Flesh, you can now absorb defensive, utility, and physical characteristics of the creature you consume. This ability could include a creature's resistances, a natural attack, natural armor, or non-offensive utility like shape change, breathe under water, climb speed, flight, etc.

You can only absorb one feature from a creature, and each feature you absorb counts as one of the abilities you know through Absorb by Experience. 

Passive features, such as a resistance or natural attack, last for 1 minute per proficiency bonus when activated and counts as one of the limited uses per long rest. Natural attacks can be used as part of the action to activate them.

Physical damage from natural attacks scales to the size of the warlock, as it is unlikely they would do the same damage with a claw they took from an ancient dragon as the gargantuan dragon did. They scale one step on the following scale based on the difference in size between the warlock and the creature of organism. If the creature's damage is not on the chart, round it down to the closest total possible. For example, 3d6 totals to 18 and would round to 2d8, which is totals 16.

4d8 > 4d6 > 2d10 > 2d8 > 2d6 > 1d10 > 1d8 > 1d6 > 1d4 > 1d2 > 1

Ease of Ephemeral Essence

At 14th level gain the following ability.

You no longer need to expend a spell slot to absorb an ability through Absorb by Experience of Essence in the Flesh.

When you kill a creature, you may immediately use the ability Essence of the Flesh as a bonus action (or reaction if it is not your turn).  If you choose not to permanently absorb one of its abilities, you may temporarily gain the use of one of its natural or passive abilities as described in Flexibility of form. For one minute, you gain access to one of its natural or defensive abilities.

You can use this ability a number of times equal to your proficiency bonus. Regain all uses of this ability when you complete a long rest.