"Light and dark, love and hate, life and death—to gaze into the chalice is to see that these things are, at their core, merely different facets of the same crystal."— Tyrael(src)
Chalad'ar, the Chalice of Wisdom is a chalice once owned by the archangel Malthael. The chalice contains living light that can never be depleted, and allows its user to see things with flawless objectivity. By peering into its depths, Malthael could see the web of connectivity that binds all things as one.
It is said that Malthael stared into the chalice for years on end while in the Pools of Wisdom, his quarter of the High Heavens. Deckard Cain believed that it was from these pools that Malthael drew from to fill the chalice.
After the destruction of the Worldstone, Malthael departed from Heaven, though he left Chalad'ar behind. After taking on the Aspect of Wisdom, Tyrael entered the realm to take Chalad'ar into his care. However, the chalice was not forged for a mortal mind, and Tyrael continued to struggle to tame his energies. Sometimes, the chalice awoke the raw power of his mortal emotions, throwing him into states of confusion, fear, and anger. Other times, an icy cold surrounded him, chilling his body. Tyrael found himself transfixed by the inevitability of his own mortality and of the death that awaits all things. However, at other times, Tyrael was able to derive positive effects from the chalice. At times, it imbued his mind and body with a profound sense of confidence, power, and euphoria, and allowed him to appreciate the connectivity of all things.
Through use of the Chalad'ar, Tyrael was able to face the truth of the Black Soulstone, that as long as it remained in the care of the Angiris Council, it would bring about the downfall of both Heaven and Sanctuary. Only humanity could be trusted to safeguard the stone, he concluded. It was a conclusion he later reflected was obvious, but he had hidden from the truth, only for Chalad'ar to painfully strip away his delusion. Such is the price of wisdom, he reflected.