Wyrmskull Throne

From Storm King's Thunder, page 237.

Description
Wondrous item, artifact.

Built by dwarven gods and entrusted to the rulers of Shanatar, an ancient dwarven empire. The Wyrmskull Throne was a symbol of dwarven power and pride for ages untold. The throne hovers a foot off the ground and is a massive thing made of polished obsidian with oversized feet — the impaled skulls of four ancient blue dragons. Runes glisten in the carved obsidian winking to life with blue energy when the throne's powers are activated.

After the fall of Shanatar, the Wyrmskull Throne fell into the clutches of less honorable creatures. A band of adventurers wrested the throne from the aquatic elf tyrant Gantar Kraok and sold it to the storm giant Neri for a considerable fortune. Neri had the throne magically enlarged and gave it to her husband, King Hekaton, as a gift, along with one of the Ruling Scepters of Shanatar, which she had found in a wreck at the bottom of the Trackless Sea. Only a creature attuned to a Ruling Scepter and in possession of it can harness the powers of the Wyrmskull Throne, which has become the centerpiece of King Hekaton's throne room in the undersea citadel of Maelstrom. Fear of the throne's power has helped prevent evil giants from challenging or threatening Hekaton's leadership.

Any creature not attuned to a Ruling Scepter who sits on the throne is paralyzed and encased in a magical force field. While encased, the creature can't be touched or moved from the throne. Touching a Ruling Scepter to the force field dispels the field, though the creature remains paralyzed until it is separated from the throne.

Any creature seated on the throne can hear faint whispers in Draconic — the whisperings of four blue dragons whose skulls adorn the throne. Although powerless, these spirits try to influence the decisions of the throne's master

Properties of the Throne. The throne has 9 charges and regains all expended charges daily at dawn. A creature that sits on the throne while attuned to a Ruling Sceptor in its possession can harness the throne's properties, which are as follows:
 * The throne gains a flying speed of 30 feet and can hover and flies where the creature wills. This property doesn't expend any charges.
 * Both the throne and the creature sitting on it can move through earth and stone without disturbing the material they move through. This property doesn't expend any charges.
 * As an action, the creature can expend 1 charge to cast Lightning Bolt (spell save DC 19) from the throne. The spell is cast as though using a 9th-level spell slot and deals 49 (14d6) lightning damage. The bolt discharges from the mouth of one of the throne's blue dragon skulls.
 * As an action, the creature can expend 2 charges to cast the Globe of Invulnerability spell from the throne. The globe encloses both the creature and the throne.
 * As an action, the creature can expend 3 charges to create a spectral image of an ancient blue dragon that surrounds both it and the throne. The spectral dragon lasts for 1 minute. At the end of each of the creature's turns, the spectral dragon makes one bite attack and two claw attacks against targets of the creature's choice. These attacks have the same attack bonus, reach, and damage as an ancient blue dragon's bite and claw attacks.

Destroying the Throne. The Wyrmskull Throne can be destroyed by breaking at least five Ruling Scepters of Shanatar simultaneously on it. This fact has never been recorded or sung of among the dwarves or any bards or storytellers, and it can't be discovered with an ability check. Characters who want to destroy the throne must go on a quest to learn the method for doing so. The throne's destruction triggers an explosion, as shards of obsidian fly out in all directions. Each creature and object within a 30-foot-radius sphere centered on the throne must succeed on a DC 21 Dexterity saving throw, taking 70 (20d6) slashing damage on a failed save, or half as much damage on a successful one.