Fiend soul

Fiend souls are those that have had more devilish or demonic energies added into them. they can grow horns, claws, grow fangs, the sort. some teiflings actually manifest this power, as well as anyone with a connection to more hellish sources of power, like some warlocks and/or their kin.

abyssal Magic

Your link to hellish powers allows you to learn spells from the warlock class. When your Spellcasting feature lets you learn or replace a sorcerer cantrip or a sorcerer spell of 1st level or higher, you can choose the new spell from the warlock spell list or the sorcerer spell list. You must otherwise obey all the restrictions for selecting the spell, and it becomes a sorcerer spell for you.

 

Fiendish rancor

Starting at 1st level, fiendish power drives you to mass violence. If you reduce a hostile creature to 0 hit points, you can use you reaction to move up to half your speed and make another attack or cast another spell. Once you use this feature, you can’t use it again until you finish a short or long rest.

Empowered damage

Starting at 6th level, the devilish energy coursing through you can empower damaging spells. Whenever you successfully hit on a damaging spell or a creature fails a saving throw for one of your spells, you can spend 1 sorcery point to reroll any number of those dice once, provided you aren’t incapacitated. You can use this feature only once per turn.

Otherworldly traversal

Starting at 14th level, you can use a bonus action to manifest a pair of spectral bat wings from your back. While the wings are present, you have a flying speed of 30 feet. The wings last until you’re incapacitated, you die, or you dismiss them as a bonus action.

 

Additionally, you can  forgo the wings for a set of claws. whilst the claws are present, you have a climbing speed of 30 feet.

metamorphosis

At 18th level, you mutate to be like your fiendish kin. as an action once per long rest or if you use 6 sorcery points, you can metamorphize, gaining the following traits:

you gain darkvision out to a rate of 120ft, it can see through magical darkness.
your unarmoured AC includes your charisma modifier
you gain immunity to fire, poison and cold damage. Additionally you gain immunity to the poisoned condition.
your creature type changes to fiend and your size becomes large.

This lasts for 1 minute, when you drop to 0 or if you cancel it as a bonus action.

In the Character Builder, set the option for metamorphosis to Fiend to activate the bonuses for that form on the character sheet.

Fiend

you are a fiend

Humanoid

You are humanoid.