Ancient Shield Guardian

Upgradeable: This Shield Guardian is upgradeable to where every part on it may be refitted or upgraded (one at a time) during a long rest. However, you must first find or buy the materials in order to facilitate the upgrade process. These things could be from shops, Dungeons, or even Traveling merchants. Item to look for are the following: 

1. 2 intergraded reasoning Chips: These chips are highly valuable for machines. This allows for reasoning and planning provided of course if they have the mental compacity for such a thing. Their Wisdom score goes up to 14.
2. 2 intergraded information chips: These chips are highly valuable. able to give Sentience to machines. Once acquired intelligence to any kind machine goes up to 14 and it becomes Sentient
3. 1 magical Heart: A special Ore that acts like a heart giving the Shield Guardian Emotions and giving it a charisma score of 14. This also allows for its spell storing to be updated past 2 second level to level 5. 
4. 6 Adaptive plating: AC +2 and 1 Dungeon master approved armor upgrade.
5. 4 magical Gears lags: Magical Gears said to belong to a lost civilization. these gears help a machines move. Gains a reaction ability "Defensive Motion" and do to new magical gears in its lags it now has Tremor Sense range 50 feet
6. 4 magical Gears arms: Magical Gears said to belong to a lost civilization. these gears help a machines move. Gains ability to hold a weapon and now can use its Multiattack feature. 
7. 4: Magical Gears torso + neck: said to belong to a lost civilization. these gears help a machines move. Gains the Ability to turn around 360 degree and advantage on perception checks

Soul Bound. The shield guardian is magically bound to an amulet. As long as the guardian and its amulet are on the same plane of existence, the amulet's wearer can telepathically call the guardian to travel to it, and the guardian knows the distance and direction to the amulet. If the guardian is within 30 feet of the amulet's wearer, half of any damage the wearer takes (rounded up) is transferred to the guardian.

Maintenance. To regain Hit Points, the guardian must be brought to a mage to be repaired costing gold 10 gold per Hit Point or be brought to a gifted magical engineer in your party that can repair it upon a successful tinker's or black smiths tools check during a long rest.  If Hit Points hit 0, guardian falls to pieces(Head, Torso, Left and Right Arms/Legs). You can gather all pieces and bring to a mage to rebuild guardian for large sum of gold. 

Spell Storing. A spellcaster who wears the shield guardian's amulet can cause the guardian to store one spell of second level or lower. To do so, the wearer must cast the spell on the guardian. The spell has no effect but is stored within the guardian. When commanded to do so by the wearer or when a situation arises that was predefined by the spellcaster, the guardian casts the stored spell with any parameters set by the original caster, requiring no components. When the spell is cast or a new spell is stored, any previously stored spell is lost.

Multiattack after arms upgrade. The guardian makes two fist attacks.

Fist. Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 11 (2d6 + 4) bludgeoning damage.

Shield. When a creature makes an attack against the wearer of the guardian's amulet, the guardian grants a +2 bonus to a Ally's AC if the guardian is within 5 feet of the wearer. 

Defensive Motion after lags upgrade. The shield Guardian can move up to 15ft as a reaction without provoking attacks of opportunity. If this causes an attack to effect to miss, such as moving out of the reach of a foe, the attack or effect is still expended. once using this reaction, The Shield Guardian can push a willing creature within 15ft of it up to 10ft away. It then moves into the creature's space from where it was at. effectually, placing the friendly creature behind you or moving them up. This does not cause attacks of opportunity for the creature that is getting pushed.