You have Resistance to Poison damage. You also have Advantage on saving throws you make to avoid or end the Poisoned condition.

You don’t need to eat, drink, breathe, or sleep, you can complete a Long Rest in 6 hours, by having your spirit be left in a trance like state that you are fully conscious in.

You have focused your ghostly powers to grant yourself one of the benefits of your ghostly state, pick one of the following traits;

1. Ethereal Stride: You can move through objects and creatures as if they were difficult terrain, if you end your turn inside an object or creature, you will take your Proficiency Bonus d8 Force damage and be forced back to the last space you were that wasn't occupied by a creature or object, if you have another similar trait, pick which one to have active.
2. Ghostly Hover: You can control the rate at which you descent, causing you to have immunity to fall damage, and you can make yourself hover off the ground, up to 60ft above the ground, so long as you are not carrying excessive weight (e.g. another creature of similar size).
3. Undead Resilience: Whenever you take damage, you can reduce the damage by 2 times your Proficiency Bonus, this can be done an amount of times equal to your Proficiency Bonus, refreshing on a Short or Long Rest.

Your physical condition is weakened from the sheer toll of avoiding the supposedly inescapable pull of the beyond, your Hit Point decreases by 1, and it decreases by 1 again whenever you gain a level.

Escaping death that easily doesn’t come without consequences, death constantly pulls at you, causing you to be unable to escape it without focus, don't remove Failed Death Saves when becoming Stable or regaining HP, instead keep them, and reduce them only when resting, 1 when Short Resting, and 2 when Long Resting.