The Fused Shadow is an ancient relic of the Twili people from before they were banished, created during the Interloper War.  In its base form, it offers some magical abilities, but its power truly shows and grows with the collection of the other 3 separated parts of the Fused Shadow.

You have found Fused Shadow has taken a liking to your powers and attuned to you.  Nothing you do seems to get it to unattune from you and it is stuck on your head (DM discretion on how to remove it), covering one of your eyes.  However, drawing such a minimal amount of magic from your latent power, such that it does not affect your conscious abilities, it allows you to see normal through the helmet from the covered eye.

Eye of Twilight.  The Fused Shadow covering your eye lets you see in magical ways.

If your race does not have Darkvision, you gain a 60 ft Darkvision in that one eye, allowing you to see in dim light within the radius as if it were bright light, and in darkness as if it were dim light, while the Fused Shadow is attuned to you.

If your race has Darkvision, you gain Improved Darkvision, doubling the distance of your darkvision in that one eye while the Fused Shadow is attuned to you.

As a bonus action, you can say the command word and see normally in darkness, both magical and nonmagical, to a distance of 120 ft in that one eye while the Fused Shadow is attuned to you.  Saying the command word again deactivates it. 

Notice Me Not  Fused Shadow knows it stands out and has a way to hide.  As an action, you can say the command word and Fused Shadow becomes invisible.  Saying the command word again deactivates the invisibility.

Sentience. Fused Shadow was a Chaotic Evil artifact with an Intelligence of 12, a Wisdom of 15, and a Charisma of 15, but the thousands of years since its last access to magic to fuel itself, and the thousands of years before that since it was created, has degraded its sentience to near nothing.  Only extreme emotions can nudge it from its stupor, but it only truly reacts to negative emotions.

Should the attuned creature feel such extreme negative emotions, the Fused Shadow may choose to communicate telepathically with the wielder, mostly to egg them on to delve deeper into those emotions, or to pass along the hate and bloodlust its creators infused it with.  It speaks in undercommon (Twili) in a deep, gravely voice, has hearing out to 60 feet, and can sense the presence of creatures in the same distance.

Personality. Fused Shadow holds a hatred for Hylians, as they were the enemy of its creators.  On the rare occasion that Fused Shadow is pulled from its lethargy, it reacts negatively to the presence of any creatures that resemble Hylians (DMs discretion), to the point it floods your head with rage and bloodlust to destroy said creature(s).  Should this happen, you must succeed a DC 15 Wisdom saving throw or be overtaken by the rage until you can be jolted out of it.  You can reroll your check every 30 seconds. 

The 4 Pieces (Optional).  The Fused Shadow is broken into 4 parts.  You have the first one attuned to you already.  If, along your travels, you come across other pieces, they can be reintegrated back together, though in the minimal power state, the other pieces store in their own pocket dimension.  Using an action, you can pull out and reintegrate or dismiss the additional pieces.

Each additional piece helps amplify your magics and, once you have collected the 2nd piece, you can use Fused Shadow as a spellcasting focus.

Each additional piece adds +1 to your spell attacks and damage.  Once you have 3 pieces equipped, your spells ignore half cover.

If all 4 pieces are brought out, you are transformed into the Fused Shadow Monstrosity for 1 minute or until the Hunger for Pain ability takes effect.  You do not have access to any of the Legendary Resistances or Legendary Actions.  Once you revert in form, you are unconscious and gain a level of exhaustion.

Notes: Sorcerer with levels in Fused Shadow Magic