When a character reaches 0 hit points or when an attack against a demigod is a natural 20 you lash at them with an unavoidable beam of Abyssal energy. This burst of energy automatically does 15d4 radiant fire damage.

Because of your readiness for a fight, any weapon your father has used, you can become temporarily proficient with and upon 3 uses your proficiency becomes permanent. When permanent, the weapon becomes astral bound to you and can be summoned unto they have been broken

Due to your father’s companionship with the beast Cerberus, all spawn of Hades have a dedicated Cerberus Pup that manifests when close to death. It returns  them to half hp and will add  One of 3 specified damage types 

Fire,Cold,Psychic,poison, lightning, Acid

You can speak, read, and write Common, Abyssal, Minotaur, Celestial, infernal  and one extra Language of your choice. Hades spawn typically learn the languages of other peoples they deal with, including obscure dialects. They are fond of sprinkling their speech with words borrowed from other tongues: Orc curses, Elvish musical expressions, Dwarvish military phrases, and so on.

If hit 3 times by an opponents weapon, these demigods become temporarily proficient with that weapon. If a fourth hit is attempted and dishes they are granted advantage on DEX & STR if they attempt to take their foes weapon away. At level 14 they may conjure an abyssal mirror image of any weapon that has hit them 3 times for up to an hour a day

You call forth the earth shaking power of your father and rip apart the very ground beneath your enemies feet. You may close up to 4 attacking creatures within 20 ft of each other and catch their feet in the ground to hold them in place. (3d6 piercing dmg) You may also conjure the flames of Hades to scorch their entrapped limbs (4d6+2 fire damage)

You can use your bonus action to open up a rift within 120 ft of you that is 25 ft long, it becomes difficult terrain and is 10 ft deep, you can then close the rift with an action, and creatures in the rift have to make a Dexterity saving throw or take 1d8 bludgeoning damage and be restrained. On a success they only take half damage, and is not restrained. At the end of each of their turns they can make a Strength saving throw. The length and damage increase to 30 ft and 2d8 respectively at 5th level, 45 ft and 3d8 at 10th level, and 60 ft at 4d8 15th level. At the start of each of your turns, roll 1d12, you regain the ability to use this if you roll a 12

At the beginning of each battle you roll a d6 to determine the amount of skeletons you may summon for combat. The skeletons have an AC equal to yours and depending on The number 1/6 of your stats. You may only use this ability 3 times a day, resets at dawn. At level 4 your skeletons become an extension of you and as such act and look like you. At level 8 the skeletons may become corrupted souls pulled from Hades. Any life they take raises their collective strength +2 and their souls are bound to you, giving you their memories and proficiencies. At 12th lvl you may roll a d8 and summon that many skeletons, bound souls or both. At 16th level you can summon individual dead that you have taken to lead your eternal army of darkness. This general can be sent with a squadron of up to 8 soldiers to do a test you require. You may still summon up to 8 in battle at a time. At lv 19 you may summon up to 4 generals to lead your armies and follow your command

Once per day you may speak a command word and  all dead and undead creatures  within (roll 1d100) miles will fall under your command. 

Because of your godly heritage, you have been born immune to Necrotic, radiant and Fire damage

When you are in dim light or darkness, as an action
you can teleport up to 30 feet to an unoccupied space
you can see that is also in dim light or darkness. You are also granted Darkvision with a limit of 40ft where everything appears to be fully lit to you but others still need a bright light to see

Because of your heritage , once a day you may choose to use one Ether ability from your father

1. Necromancy, (raise the dead) for 1 hour, you conjure 3
undead servants or if you are in a shadow you can
shadow jump into another shadow 50 ft away 1 Day
recharge
2. You can summon a jewel destined to curse and
impress anyone or if you are in a shadow you can
shadow jump into another shadow 50 ft away 1 Day
recharge

Children of Hades have advantage on stealth throws.

Children of Hades have advantage on death saving
throws.

Due to your father being Hades, one of the big three gods ruling over the three major domains, your scent is strong and easily recognizable by monsters, and mythical creatures. Monsters and other mythical creatures would know of your general location once you are within a one-mile radius of them. Furthermore, you roll with disadvantage with Stealth checks when hiding from monsters who have the ability to smell.

You have proficiency in Intimidation, resistance to
necrotic damage, and cannot critical fail on your Death
saving throw.

You know either Toll the Dead or Chill Touch cantrip.
If you are in a place of shadows, you may use an action to bring 2 willing creatures along you to travel and emerge from another point of shadows with a distance equal to your (Constitution modifier plus your character level) times 10ft. If the creature is unwilling, it must succeed a Dexterity (Acrobatics) contest against you, or be teleported. The first time that you shadow travel, you make a Constitution saving throw with a DC of 10. On a failure, your exhaustion level is raised by 1, and the DC is raised by 5 for the next time you attempt to shadow travel. On a success, the DC is raised by 2 instead. The DC resets to 10 after taking a long rest.

you do not need to sleep, but instead refocus the connection you have to your bond. When you take a long rest you must spend at least 6 hours to refocus, during this time you are still aware of the world around you honing your connection to the underworld and your father. This connection is how you draw the necessary souls and proficiencies of slain foes and the powers of Hades

Due to your divine heritage you may remove and store souls within yourself for a boost to your own defense or to aid others. You may hold up to 5 souls and can be used to force the enemy to refill an attack. When done the lower roll must be used. 

In order to store more souls, you may imbue your weapons with them to deal +5 psychic damage. By imbuing these souls you become proficient with said weapon until the weapon is broken or the souls are removed.

Upon death, If  your body can no longer be used, your soul will return to the world in the eyes of a recently dead creature your size who has given up their will to live. Over the period of one week, you revitalize the body and make it yours, making alterations and changes as you wish