(And there really aren't any spoilers, because their legend is spread far and wide.)
(AKA Godsbane; The Doom of Divinity)
From the days of the Dawn War on Khaldun, many are familiar with the tale of fallen Sorg and his magnum opus, the Ydinikuisuuden or Crux of Eternity.
Fewer are familiar with its elemental counterpart, the Godenschemering, or Godsbane.
The forging of the Eternal Cross was the death knell of the Primordial faction in the Dawn War, and it prompted a war of escalation. A Primordial artisan forged the Doom of Divinity, a dagger utterly deadly to deities. A potent magical weapon in its own right, the dagger unerringly seeks deities' weak points and severs the ties between them and the belief that sustains them. After the Primordials were defeated, it is said that the gods themselves erased as many records of its existence as they could (the reason why nobody is quite certain whether it actually slew any gods) and hid it in a deathtrap dungeon. To keep it away from their enemies, it is neither in the Astral Sea nor the Elemental Chaos, but hidden somewhere in the world.
In game terms, the Godenschemering acts as a +6 dagger. It is Chaotic (Chaotic Neutral if using the 9-point alignment) with Intelligence 20 and Ego 28. It can speak and communicate telepathically, able to speak Common, the Chaotic (Neutral) alignment language, and the language of the Primordials. In combat, it deals standard damage for a +6 dagger, and an additional 1d3 cold damage. It deals double damage to fire-based creatures, detects sloping passages within 20 feet, detects divine entities within 60 feet, and detects secret doors within 30 feet. It is vampiric, healing half of all damage dealt to a victim with each attack (up to the attacker's maximum, of course). Finally, it allows the user to turn invisible once per day for 40 minutes.
Notably, a successful attack with Godenschemering targeted at a deity has a 95% chance of destroying that deity outright.
The dagger seeks the utter destruction of all divine entities, everywhere. With its high Intelligence and Ego, few can resist the dagger's demands, and those who attempt to defy its orders are overtaken by the dagger's personality and forced to begin hunting the most dangerous game.
It is the DM's decision whether the dagger's god-smiting effect has any effect on demigods, angels, and other associated divine servitors.
The Axes of Evil
One of my Spelljammer players from something something Blogstrorum made a backstory/future quest request, and this popped out.
A legendary item from Rockulon Prime, the Axes of Evil are a pair of battle axes forged by the drow and supposedly masterminded by the ancient drowtech supercomputer known as The Wykydtron. They were used in the Drow War, only to be lost until they reappeared in the hands of the infernalist Wraithsmasher bloodline. The axes' whereabouts are unknown after that, but it rumored that they were lost somewhere in the frozen north, awaiting rediscovery by an intrepid soul.
The Axes of Evil are always found together, and are a pair of +2 battle axes. Like some magic swords, these axes are sentient and sapient, communicating with the wielder by way of speech and telepathy; the pair of axes has Intelligence 17 and Ego 14. They are Chaotic (Evil), and have the ability to speak and communicate telepathically, communicating in Common, the Chaotic (Evil) language, the language of Elves, and the silent language of the drow (this last it can convey with its telepathy).
If the axes win a personality conflict against a wielder, they curse the character — a cursed character is driven berserk in combat, attacking the nearest creature until no creatures are living within 30 feet. A character so cursed will automatically have the Axes of Evil appear in his hands at the beginning of each combat, and will be forced to save vs. magical device (or equivalent saving throw, such as AD&D's Rods, Staffs, and Wands) or become berserk each time this happens.
The curse can be lifted through an exorcism or wish spell.