You may have inherited a blessing, or more likely a curse, but either way you seem to be changing in an unpleasant way...

Amphibious

You grow large noticeable gills on your neck or behind your ears, which enables you to breath water even while unconscious.  The skin on your fingers tightens and your nails thicken and grow to points, your skin becomes slimy and your completion poor, and your teeth are discolored, jagged, and sharp.
You can attack with your claws and teeth, and you gain darkvision to 60 feet.

Illusory Appearance

You are growing uglier, misshapen, even horrifying.  You are able to maintain an Illusory Appearance similar to Disguise Self with the strength of your maximum spell level to outwardly appear as you did before this transformation began.  Other Hags recognize your transformation, which may cause them to be threatened by your presence or look down on you as an inferior, it is unlikely that they would treat you as an equal for the first few hundred years.

Regardless of your character's race, you are now considered a fey for purposes of detection and spell targeting.

Haven

At level 14 you chose one of the three below domains as that which shall be your eventual haven.

One with the Forrest

Your skin is gray, dry, and cracked, the whites of your eyes are a sickly yellow, and much of your flaky skin hangs loose from your spindly limbs.
You are able to mimic the sounds of animals and people you have heard.  You are able to pass without trace at will.  You can Tree Stride a number of times equal to your Dexterity modifier per short rest at the cost of 10 movement.

One with the Night

Your skin is black as night and does not reflect moonlight, your hair has turned white, and looking down your throat is like peering into the abyss.
You are able to enter the Ethereal Plane or return from it to the Material Plane twice per long rest per the Plane Shift spell effect.
You can Shadow Step to teleport from one area of darkness to another as a bonus action a number of times equal to your Dexterity modifier per short rest.

One with the Sea

Your skin is slick and scaly, your hair resembles seaweed and covers your slender frame, and your shiny eyes seem like that of a doll.  Although you can hide your true form under a veil of illusion, you are cursed to forever appear shocking.
You can use your shocking appearance to afflict charmed or frightened conditions on those that see it.  Once you have frightened a target then you may, once per long rest, attempt to use your Death Glare to cause the target to immediately drop to 0 hit points.
Your illusory form appears slightly unusual as well, your approximation of what you would look like if you had not been transformed and slowly grows older and less attractive.

Unnatural Connection

At 18th level, chose one of the three below connections in which your influence has extended.

Covenant

You can join yourself with two or more other spellcasters and form a coven, this consumes one attunement slot for each of you.  This ritual requires all member participate for one hour, if you conduct this ritual again then your previous coven will be dissolved unless one of it's other members also possesses this ability.  It will also be dissolved if any other member leaves the coven, that is if they are alive and remove this attunement, and no remaining members have this ability, it does not end automatically as a result of your death.

While three members of your coven are within 30 feet of one another, then one may use their bonus action to transfer an unused spell slot from one of the others to the third member.  All three have to agree, the one performing the transfer, the one giving the spell slot, and the one receiving the spell slot.  Any member of the coven may perform this action on either of the other's turns as long as they did not use their bonus action on their previous turn.  All members of your coven gain this ability, you are not required to be one of the three if there are four or more members in the coven.

While another member of your coven is within 60 feet of you and casts a spell that targets only themself, then as an action on your turn you may cast the same spell targeting only yourself.  To copy the spell you must have a spell slot available of the same level and when cast it uses your modifier for the attribute they use for spellcasting.

Loathsome Limbs

You die only if you drop to 0 hit points and can’t regenerate (if you are hit with cold, fire, or necrotic damage before you can recover any hit points).  Any one of your severed body parts may regenerate your whole.
Whenever you take at least 15 slashing damage at one time, roll a d20 to determine what else happens to your limb:
1–10: Nothing else happens.
11–14: One leg is severed from you if you have any legs left.
15–18: One arm is severed from you if you have any arms left.
19–20: You are decapitated.  If your body dies, so does your severed head.

If you have a severed body part you can reattach it over the course of a short rest.  You can regrow a missing limb over a long rest.  In either case you must have the part that it attaches to, you cannot regrow or attach an arm if you are only a head with no body.  When a part is regrown the missing one dies if it was still alive.

A severed part acts on your initiative and have one action and their own movement.  A severed part has your unarmored AC and takes one hit die worth of your hit points with it when severed.
A severed leg is unable to attack and has a speed of 5 feet.
A severed arm has a speed of 5 feet and can make one unarmed/natural attack on its turn, with disadvantage on the attack roll unless you can see the arm and its target.  When you lose an arm, you temporarily lose the multiattack action (if you have it).  The arm can grab or manipulate objects, in a limited capacity, and can cast cantrips with no verbal components.
If you're decapitated, you lose your bite attack and your body is blinded unless your head can see it.  Your severed head has a speed of 0 feet.  You can make a bite attack but only against a target in your head space, and your head can cast spells with no somatic components.
Your speed is halved if you are missing one leg.  If you lose both legs, you fall prone.  If you have both arms, you can crawl at your climbing speed.  With only one arm, you can still crawl, but your climbing speed is halved.  With no arms or legs, your speed is 0 and you can’t benefit from bonuses to speed.  You can cast spells as normal if at least one arm and head are within 10 feet and line of sight, and any required material components are in contact with a living body part also within 10 feet and line of sight or your head.

Witch's Tools

You learn how to create the following:
A trinket out of bone, of which you know the precise relative location up to 10 miles away, if you create a new one then the previous one ceases to be a magical item.
A trinket coin out of iron which allows the holder and you to Message one another up to 10 miles away.  You can have three of these tokens active at a time, and you know the rough direction and distance of these tokens.  You can deactivate one from any distance at any time.
A enchanted broom of flying that is only usable by you and consumes one of your attunement slots.
A trinket in the form of a black gem that can cure you of any disease with a touch.
A soul bag, made from the flesh of a humanoid, and used to trap souls of evil creatures.