Embodiments of Absolute Law & Chaos in weapon form
Before the Gods were the Primal Powers, Law and Chaos, and the Lords thereof. These ever-warring entities created weapons embodying their philosophies; Ancorir, the Mace of Absolute Chaos, and Zero-One, the Sword of Absolute Law.
At the beginning of Time, the Lords of the Primal Powers retreated beyond the Multiverse, leaving the Primal Weapons behind. They took great pains to conceal them, knowing that no creature bound by Time and touched by Good or Evil could express pure enough Law or Chaos to endure their touch for long.
Ancorir remained secure, but Zero-One was discovered and fell into the hands of Zerhal Avara, who carved a position in Avernus under Bel. The Dragonslayers retrieved it from him, and placed it in the Hallows, created by all the Gods as a safe place for eternity.