The Soulcrown:

The Soulcrown is oddorned with five spirelike features of a obsidian colour. Each has a gem, the gems can be removed and attached to the crown but must be in the correct slot.
Once the crown has been equipped it is automaticly Attuned, if no attunement slots, the weilder will have another attuned item automaticly unattuned.

If the crown is removed, the weilder automaticly dies.

These necromantic gems can steal the souls of the dying within a radius of a gem.
A gem can be Linked to a Living Humanoid creature within 90 Feet. The Living Humanoid will gain a point of exhaustion each dawn.

Exhaustion Levels
Level Effect
1 Disadvantage on ability checks
2 Speed halved
3 Disadvantage on attack rolls and saving throws
4 Hit point maximum halved
5 Speed reduced to 0
6 Death

If the Living Humanoid Creature dies in result of the Link, its soul will be transferd into the gem.

Gems within the crown can transfer Souls within any gem into another also within the crown.

The Blood Gem: (Required: Free Action)

Souls within the Bloodgem can be transferd into Componets of value up to 1000gold for a spell/Enchantment or crafting.
Each soul can only be transformed into one component up to the given value, it cannot be split into diffrent components.

The Power Gem:

Souls within the Powergem can be used to cast a 5th level version one of the following spells: (Required: Action) (No componets required)

Fireball
Wall Of Fire 
Web Of Fire 
Fire Shield 

The Shadow Gem (Required: Bonus Action) (No componets required)

Souls within the Shadowgem can be used to cast Misty step, when cast, the caster is granted Greater Invisibilty.

The Mystic Gem: (Required: Action) (No components required)

Souls within the Mysticgem can be used to cast one of the followning spells:

True Seeing
Scrying
Legend Lore
Teleport

The Death/Life Gem

The souls within the Deah/Lifegem can be used to cast one of the following spells: (Required: Action) (No componets required)

Revivify: 
Circle Of Death: 
Raise Dead:
Summon Undead:(5th level) (Can be cast as a Reaction if a humanoid dies within 90 feet, in vision, of the the holder of the gem)