Magic Items

Ring of Invisibility
Ring, legendary (requires attunement)
While wearing this ring, you can turn invisible as an action. Anything you are wearing or carrying is invisible with you. You remain invisible until the ring is removed, until you attack or cast a spell, or until you use a bonus action to become visible again.

Gauntlets of Ogre Power
DMG
p171
Wondrous item, uncommon (requires attunement)
Major tier
Your Strength score is 19 while you wear these gauntlets. They have no effect on you if your Strength is already 19 or higher without them.

(reminiscent of your shield guardian modifications),

Illithid tech flavour

Wondrous item, rare (requires attunement by a sorcerer)
1 lb.
This writhing crystal is steeped in the warped essence of the Far Realm. As an action, you can attach the shard to a Tiny object (such as a weapon or a piece of jewelry) or detach it. It falls off if your attunement to it ends. You can use the shard as a spellcasting focus while you hold or wear it.

When you use a Metamagic option on a spell while you are holding or wearing the shard, you can cause a slimy tentacle to rip through the fabric of reality and strike one creature you can see within 30 feet of you. The creature must succeed on a Charisma saving throw against your spell save DC or take 3d6 psychic damage and become frightened of you until the start of your next turn.

Ring, very rare (requires attunement outdoors at night)
Major tier
While wearing this ring in dim light or darkness, you can cast dancing lights and light from the ring at will. Casting either spell from the ring requires an action.

The ring has 6 charges for the following other properties. The ring regains 1d6 expended charges daily at dawn.

Faerie Fire. You can expend 1 charge as an action to cast faerie fire from the ring.
Ball Lightning. You can expend 2 charges as an action to create one to four 3-foot-diameter spheres of lightning. The more spheres you create, the less powerful each sphere is individually.
Each sphere appears in an unoccupied space you can see within 120 feet of you. The spheres last as long as you concentrate (as if concentrating on a spell), up to 1 minute. Each sphere sheds dim light in a 30-foot radius.

As a bonus action, you can move each sphere up to 30 feet, but no farther than 120 feet away from you. When a creature other than you comes within 5 feet of a sphere, the sphere discharges lightning at that creature and disappears. That creature must make a DC 15 Dexterity saving throw. On a failed save, the creature takes lightning damage based on the number of spheres you created. (4 spheres = 2d4, 3 spheres = 2d6, 2 spheres = 5d4, 1 sphere = 4d12)

Shooting Stars. You can expend 1 to 3 charges as an action. For every charge you expend, you launch a glowing mote of light from the ring at a point you can see within 60 feet of you. Each creature within a 15-foot cube originating from that point is showered in sparks and must make a DC 15 Dexterity saving throw, taking 5d4 fire damage on a failed save, or half as much damage on a successful one.

Very Rare
Armor (scale mail), very rare (requires attunement) Dragon scale mail made of the scales of a red dragon. While wearing this armor, you gain a +1 bonus to AC, you have advantage on saving throws against the Frightful Presence and breath weapons of dragons, and you have resistance to fire damage. Additionally, you can focus your senses as an action to magically discern the distance and direction of the closest red dragon within 30 miles of you. This special action can’t be used again until the next dawn. This was once the armor of Carmine, an orc paladin of the Bloody Hooves. She didn’t survive into the final set of caverns to have her soul entombed to wait for Zariel’s return.