You gain advantage with any "positive" rolls with animals (such as taming or calming down). Also you gain proficiency in animal handling.
Animals might come to you out of their own free will to just check you out ( bird landing on your head / cat and dogs sleeping near you or sniffing you / etc. )

You gain regeneration that is equal to your level + prof bonus + con midifier once your HP is half or lower and when it's bellow 10 you add 1d4 to it. It works every round untill your HP reach half of its full amount.
Also once per long rest you can use an action to activate your regeneration and its equal to your level + prov bonus + con modifier + 1d6 and it works for 2 rounds. The number of times you can use this trait incerases by one at level 5 / 10 / 15 / 20

You gain 3 ability points and add them in any combination to STR / CON / DEX. With this feature ability score can't go above 21

Due to your isolation and "weird vibe" around you you have disadvantage on persuasion rolls but depending on your relation this can change.

you give out a "scary vibe" (intimidation prof) and people might be scared of you depending on your relation (rolling with advantage)

You gain acid or poison resistance of your choosing and radiant damage vulnerability.

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 discern colors in that darkness as shades of gray.

there is a command word / special action / broken mind control collar inplanted in your neck that if activated in some way might control you again (Player and DM choosing)

There is a condition (sound of metal / taste of blood / certain name )that makes your roll WIS saving throw and if failed you become frightened untill you are calmed down by friendly creature with charisma or roll succesfuly.
Can also give violent split personality disorder if failed too many times or caused too many times ( DM discresion ).

Your walking speed is 35 feet / swimming speed 20 ft / climbing speed 20 ft