|* The Heart of Ahriman|
Its base item type is a luckstone and it also has exactly the same properties that regular luckstones have. When carried, it confers stealth. As an intelligent artifact, it will resist curses, a useful property for a luckstone in particular, given the negative effects they have when cursed.
The most useful feature it has is that when invoked, it toggles levitation on or off. While levitating, you can use the > key to return to the ground, as with a potion of levitation (you can also just drop it, and pick it up when you land). Also as with the potion, this ends the levitation effect, and you must wait until the artifact is able to be invoked again in order to return to the air. As a levitation technique, the Heart is preferable to a supply of potions, but less desirable than the ring of levitation or boots of levitation.
Attempting to name an ordinary luckstone as The Heart of Ahriman always makes your hand slip and gives it another name. You could exploit the naming artifacts bug and try to name any unidentified gray stone as The Heart of Ahriman; if it succeeds, then you know that it was not a luckstone. Together with kicking (to detect loadstones) and rubbing (to detect touchstones), this 'bug' provides a surefire way to distinguish any unidentified gray stone.
In Robert E. Howard's novel The Hour of The Dragon, the Heart of Ahriman is a powerful artifact, the one thing that can allow a man to stand against the powers of Xaltotun.
The other three drew in their breath sharply, and the dark,
powerful man who stood at the head of the sarcophagus whispered:
"The Heart of Ahriman!" The other lifted a quick hand
for silence. Somewhere a dog began howling dolefully, and a
stealthy step padded outside the barred and bolted door. ...
But none looked aside from the mummy case over which the man
in the ermine-trimmed robe was now moving the great flaming
jewel, while he muttered an incantation that was old when
Atlantis sank. The glare of the gem dazzled their eyes, so
that they could not be sure what they saw; but with a
splintering crash, the carven lid of the sarcophagus burst
outward as if from some irresistible pressure applied from
within and the four men, bending eagerly forward, saw the
occupant -- a huddled, withered, wizened shape, with dried
brown limbs like dead wood showing through moldering bandages.
"Bring that thing back?" muttered the small dark man who
stood on the right, with a short, sardonic laugh. "It is
ready to crumble at a touch. We are fools ---"