Nabu vs The Vishanti
The Vishanti:
The Vishanti are Agamotto, Hoggoth, and Oshtur, three benevolent extradimensional entities possessing vast mystical power, who bestow mystical knowledge and power upon sorcerers who invoke their names and whom they consider worthy. They are the beings whom Earth's sorcerer supreme, Doctor Stephen Strange, most often invokes to grant additional power to his spells.Very little has been revealed about the Vishanti themselves. Presumably they are indeed three separate beings, although one text has referred to Agamotto as one of the "aspects" of the Vishanti. On the few recorded occasions that the three Vishanti have manifested themselves together to human beings, Hoggoth has appeared as a mans head, Oshtur as the head of a beautiful young woman, and Agamotto as the head of a catlike being. On one of these occasions Agamotto resembled a lion, while on another he looked much like a tiger. It is not known what resemblance these manifestations may bear to the Vishanti's true forms. When Doctor Stephen Strange has visited Agamotto's own dimension, Agamotto has appeared to him as a gigantic caterpillar. In fact, Agamotto explained to Strange that this was not his true form and that he had made himself an image from Lewis Carroll's "Alice's Adventures in Wonderland" that he had seen in Strange's mind Agamotto has also been pictured as a being resembling no creature on Earth.
Hoggoth is often called "hoary Hoggoth," presumably indicating that he is of great age. Agamotto, however, has claimed to have existed before the creation of the Earth. Hence, if Hoggoth is indeed the eldest of the Vishanti, he is older than most other known beings in the multiverse. Sorcerers speak of "the hoary hosts of Hoggoth" and sometimes invoke the hosts themselves in casting spells. This fact suggests that Hoggoth's hosts themselves have existed perhaps as long as Hoggoth himself and that they too can bestow mystical power. No more is known about the hosts of Hoggoth, however.
Oshtur is often called "omnipotent Oshtur." This name suggests that she may be the most powerful of the three Vishanti. However, it is clear that Agamotto himself is one of the most powerful known mystical beings. On one occasion Doctor Strange invoked both Hoggoth and Oshtur in casting a spell against Agamotto, but the spell failed. Possibly this incident indicates that Agamotto is more powerful than either Hoggoth or Oshtur, or perhaps only that the other two Vishanti chose not to help Strange against Agamotto (in any event, though Oshtur clearly possesses vast power, she is presumably not literally omnipotent.) The fact that Oshtur is also addressed as "gracious lady" may indicate that she has a kindly and noble nature.
Of the three Vishanti, the most is known about Agamotto the All-Seeing according to one account, Agamotto was the first sorcerer supreme of the Earth dimension. Considering that Agamotto claims to be older than the Earth itself, and that he appears to be of other dimensional origin, this account may not be entirely accurate. However, Agamotto may indeed have himself acted directly to protect the Earth dimension before the rise of its first native sorcerer supreme. Agamotto is known to be the creator of the Amulet of Agamotto, which contains the Eye of Agamotto, which can generate a powerful beam of "white" magical energy. The Amulet of Agamotto is traditionally in the possession of the Earth dimension's principal opponent to the sinister mystical being, Dormammu. Currently the amulet is the principal weapon in the possession of Dormarnmu's arch foe, Doctor Stephen Strange.
VS
Nabu:
Dr. Fate's origins begin over 10 billion years ago. Here, not long after the formation of the universe were born two elemental forces — the Lords of Order and Lords of Chaos. came into beingn of universe struggle for supremacy. One group becomes known as Lords of Order, while the others are Lords of Chaos. (Who's Who Update '88 #2) On the world called Cilia, the Lords of Order manifested themselves as the first sentient race in the universe, a race of energy beings. After millennia, circa 3500 BCE, one of the Lords of Order, descends to Earth from Cilia and became Nabu the Wise, an advisor to the pharoahs of ancient Egypt. (JSA #42)Nabu became the keeper of several powerful talismans. In the 26th century BCE, he created the Scarab of Kha-ef-re with the help of a time traveler from the 20th century. This was an attempt to overthrow Vandal Savage, who was at that time the pharoah called Khafre. (Regardless, the Scarab was lost for 4,500 years before being rediscovered in the 20th century by archaeologist Dan Garrett, who became the first Blue Beetle) (Time Masters #6)
Nabu's most powerful talisman, the Amulet of Anubis was created a few centuries later (c. 2025 BCE), but the circumstances are not certain. According to the devious creatures called Flaw & Child, Nabu commissioned the Amulet of Anubis from The Cutter, of the magical Gemworld. (JSA #42) Another tale asserts that in the Egyptian city of Bubastis, the mad priest Khalis slayed his followers in the name of the god Anubis, who then granted Khalis the Amulet of Anubis as a reward for his service. (First Issue Special #9) Whatever its origin, this Amulet then became home to the Lords of Order.