Your Dexterity score Increases by +1

Your Intelligence score Increases by +1

Choose +1 to any stat of your choice

Your size is medium

Accustomed to the veil of death, you have superior vision in dark and dim conditions. You can see in dim light within 60 feet of you as if it were bright light, and in darkness as if it were dim light. You can’t discern color in darkness, only shades of gray.

You  have proficiency in the Stealth skill

Your base walking speed is 30 feet

Certriex cannot sleep, nor be put to sleep, instead they enter a state of semi-consciousness, in which twice per day they must roll a wisdom saving throw to sustain their Material form. If they fail this saving throw they will be consumed by the Ethereal Plane, taking 1d6 necrotic damage and being incapacitated until they succeed the throw.

The Certriex can speak common plus one other language of your choice

At dawn of each day, a Certriex receives the ability to enter the Ethereal Plane (2x for that day). The Certriex can remain in the Ethereal Plane for up to 1 minute before being foced back to the material world. However, upon entry, take 1d6 necrotic damage and upon death in the Ethereal plane, automatically fail one death saving throw and return to the material plane.

When in the Ethereal Plane the Certriex will receive a double to base movement and immunity to bludgeoning, piercing and slashing damage from the material world. You gain the ability to transverse through objects as if it was difficult terrain, and as an action you can enter the body of a material being, (see grappling) tethering your own soul onto whomever you enter. When tethered, you gain control over all actions until the grapple is broken, however, you also take any damage the host takes. You can use an action to leave, or you are expelled when the host breaks the grapple. 

Upon leaving the Ethereal Plane, the Certriex will be surrounded by Ethereal shadows for up to 2 minutes. During this period, all enemies and the Certriex have disadvantage on melee attacks, and the Certriex's health is reduced to half his current HP until the shadows dissipate. During this time, the Certriex may use an action to return fully to the material world.

Once per voyage into the Ethereal Plane, you can use an action to perform a ranged attack that can travel to the material world. This attack is granted the sneak attack bonus. The Target is unaware of where the attack comes from. If this attack is a killing blow your action is refunded and you may perform another volley attack.