Dead King's Blade (5e Equipment)
From D&D Wiki
Weapon (greatsword), legendary (requires attunement by a spellcaster)
This greatsword has a large shining crystal embedded center of the hilt. The crystal is obviously magical and the sword draws power from it. This crystal changes throughout the day, being sapphire in the morning, ruby in the afternoon, and amethyst from dusk until dawn. The sword is ancient and once belonged to a king now long dead. The sword is made from steel with gemstones lined all over the hilt.
Wielding the sword grants a +2 bonus to attack and damage rolls with the weapon. Each crystal variation is infused with an element that gives the blade extra damage in addition to its normal attack. When the crystal is sapphire, the Dead Kings blade does an additional 1d4 lightning damage. When the crystal is ruby, it does an additional 1d4 fire damage. While the crystal is amethyst, the weapon does an additional 1d4 necrotic damage.
If the Dead King's Blade is picked up by a non spellcaster, The crystal will break off the blade and a new crystal must be made by finding a sapphire, ruby, and amethyst. Then they must be magically bound into the sword by a spellcaster for a short rest by using a level 6 or higher spell slot. Each spell slot above 6 will reduce the time needed to forge the crystal by 30 minutes.