“To solve the riddle and find the Heart of the Mountain, know only that the Heart is cradled in the roots of the Great Tree,” the elves will say.
The Heart of the Mountain is a perfectly spherical stone a little more than a foot in diameter. Its haft is a 5′ piece of wood that looks old, gnarled, and worn, but thick and sturdy nonetheless. The stone is not mounted to the haft as much as parts of the haft grip the stone.
The relic is a +3 Maul.
It requires Attunement by a Dwarf. Anyone other than a dwarf handling the weapon triggers its Rage power and instantly sets out to kill every non-dwarf present, starting with the closest person. A Charisma Save (DC 15) can me made at the end of the character’s turn to let go of the Heart, ending the effect at the end of the following round.
Raging Heart – 2/day, the Heart can trigger a Barbarian Rage in anyone holding it.
Raging Vengeance – 3/day, as an Action while Raging, the Heart can be slammed onto the ground sending energies into the earth around it. Anyone but the wielder within 40′ radius must make a Constitution Save or take 8d8 Thunder + 2d6 Bludgeoning damage and be knocked prone, half as much on a successful save and not knocked prone. This is considered a Melee Attack for purposes of adding to the damage roll. This can trigger a cave in or an avalanche if the wielder desires and is in an appropriate environment. The ground in the area buckles, creating a bowl-like depression that is 5 feet deep at its center. This area is Difficult Terrain for anyone but the Attuned wielder.
Rage Against the Machine – 3/day while Raging, the Heart will, if it strikes a structure or construct made primarily of stone or an earth elemental, do 50 points of structural or other damage and resistance of any kind will not apply.
Protection of the Mountain – The Attuned wielder cannot be caught/buried-in an avalanche, cave in, or any other moved/falling earth scenario. The Heart will provide a 10′ radius dome of safety in all such cases.
Reluctant – Anyone not Attuned to the Heart will find it very heavy and unwieldy, requiring two hands to lift it at all, and having Disadvantage with any attacks.