At the cost of a morbid ritual, an eldrathul wood elf is granted an edge above the rest of the world.

Ritual of Sacrificial Control: Wood Elven Variant

The eldrathul has always carried out a ritual sacrifice: One life for each day of power they are granted. If this ritual is not followed, they lose control of their character completely. The DM takes control of the character. With regard for personal safety and complete disregard of morals, the character consumes the most convenient brain and returns control back to the player.

The Wood Elven 'Consume Brain' action has been changed to 'Brain Stem.'

If a target is sentient, grappled, below 10 hit points, and within 60 ft:
'Brain Stem' may be used to kill the target without an attack roll (with a saving throw) and commune with the Elder. This process takes a full minute. The target may attempt to break free once per round, and is fully able to scream as much as they want.

In the event that a target is broken free from the grapple, the target begins the process of becoming an eldrathul.

If the target is below 5 hit points, the process is instant.

If the target is above 10 hit points, the target takes 1d6 damage per hit until they are below 10 hit-points.

The eldrathul wood elf is granted a choice between sparing the individual and creating an additional eldrathul, or 

The eldrathul will always hold a small part of themselves that distrusts what they are due to the memory gap that covers up what this ability may look like...

Here's what it might look like for a wood elven eldrathul;
The eldrathul Wood Elven tongue extends to the target with unnerving speed, unravelling and opening into a tube. Once it makes contact with the the skull, the wood elven eldrathul's thinner, bullet-like beak is rocketed through the tube and into the skull. The rest is easy to assume. 

Spines

While eldrathul wood elves do poses small, dainty tentacles for menial tasks, they mainly use their deadly spines to do their dirty work.

use 'Paralytic Spine' (1 spine until regrowth) to prompt a constitution save, DC 14. If a target is below 12 hit points they are paralyzed for one minute, otherwise on fail the target's throat closes and they are poisoned. Time to unconsciousness depends on how long the target can hold their breath. the effect lasts a maximum of 5 minutes, and if the target is not cured somehow within 3 they take -1 to INT until a spell like Lesser Restoration is cast or something else of the DMs choice (neuron death due to asphyxiation).

use 'Spine Regrowth' reaction to re-grow spines (roll a d6, 3 or above is a success)
use 'Spine Shot' (6 spines until regrowth) to shoot a spine, dealing 1d8 damage.

use 'Tentacle Grasp' to interact with objects under 1 lbs remotely within 10 feet. If prompted for strength checks using these limbs, use the appropriate modifier for half of your total strength score rounded down.

Eldritch Lineage: Appearance Change

Eldrathul Wood Elves combine Cthulian ancestry with that of their own. As an effect of their otherworldly heritage, their more inland-based desires brings them differing looks. While their hair is still made of much smaller, lighter, and quieter tentacles, its much less obvious that they are a Cthulian being. With the creative use of a hat, they might even pass as a Tiefling.

Natural Armor and Camouflage

Eldrathul Wood Elves are covered in tiny, multicolored spines. As they rotate, they change colors. This gives them an edge to stealth, and an immunity to slashing damage.

+2 to stealth rolls, immune to slashing damage

Eldrathul Traits:

Timeless Existence

Eldrathul enjoy an extended lifespan, often living for several millennia. This longevity allows them to accumulate vast stores of knowledge and arcane prowess.

Lost In Time

Once an eldrathul consumes its first mind, the Great Old Ones grant either their muscle memories or better compatibility with the infection. Either way, they also grant the eldrathul their thicker rubbery skin.
+6 to CON or DEX,
Resistance to piercing and slashing damage.

Secluded Enclaves

Eldrathul tend to establish isolated and secretive communities, often located near ancient, submerged ruins or coastal regions touched by the eerie presence of the deep sea.

Amphibious Nature

Due to their association with the sea, eldrathul have a natural affinity for aquatic environments. They are expert swimmers and can breathe both in air and underwater. Swim speed is equal to walking speed.

Insomniac

Need for sleep is negated

If an exhaustion level is gained, sleep can still help.

Dark Vision

Eldrathul live in the shadows, and have adapted accordingly. 60 ft