Orb of Plasma
Wondrous Item – Legendary (requires attunement)
As you place a hand on the Orb of Plasma, you feel immense energy flow through you. While attuned, your spell save DC and spell attack bonus each increase by 2 and you have advantage on all concentration checks. Additionally, you are immune to lightning damage. The orb contains 2d4 charges which can be expended to inhabit the Plasma Dragon. After all the charges are used, the orb breaks.
As an action, you can expend a charge and enter a meditative trance during which you become incapacited as you conjure forth a Plasma Dragon (same stats as an Adult Blue Dragon) to a point you can see within 500 feet. You see through the eyes of the dragon and control it on your turn, though you do not have legendary actions. You can dismiss the creature as an action, however if it dies before being dismissed, the Orb of Plasma shatters and the dragon dies. If concentration drops or the creature is dismissed, it cannot be conjured again for 3d4 days. You may control the dragon as long as you desire, but every hour you must make a competing Wisdom saving throw against the creature (it has +7). On a failed save, Orb of Plasma shatters and the dragon regains full autonomy…also it’s angry and knows your location.