There are two different research on Abgal. I will put down the more popular version.

Classification: Mythical

The Sumerian people of Mesopotamia believed in the seven wise deities that attended to the god Enki. They were also called the Apkallu by the Akkadian people. Some ancient texts mentioned them as the Ummanu. They were often described as being upright like mankind, but having fish heads. (Some say they even had bird heads.) They represented wisdom and knowledge. Here are the names of the seven sages:

Uanna, "who finished the plans for heaven and earth",

Uannedugga, "who was endowed with comprehensive intelligence",

Enmedugga, "who was allotted a good fate",

Enmegalamma, "who was born in a house",

Enmebulugga, "who grew up on pasture land",

An-Enlilda, "the conjurer of the city of Eridu",

Utuabzu, "who ascended to heaven".

It also appears that the Sumerian people believed in divine right to rule, which many ancient civilizations did. To support this, there would be an Abgal sage to attend to each king. Here is a list of the kings and their sages:

During the reign of Ayalu, the king, [Adapa]† was sage. During the reign of Alalgar, the king, Uanduga was sage. During the reign of Ameluana, the king, Enmeduga was sage. During the reign of Amegalana, the king, Enmegalama was sage. During the reign of Enmeusumgalana, the king, Enmebuluga was sage. During the reign of Dumuzi,the shepherd, the king, Anenlilda was sage. During the reign of Enmeduranki, the king, Utuabzu was sage. After the flood, during the reign of Enmerkar, the king, Nungalpirigal was sage, whom Istar brought down from heaven to Eana.
During the reign of Gilgamesh, the king, Sin-leqi-unnini was scholar. During the reign of Ibbi-Sin, the king, Kabti-ili-Marduk was scholar. During the reign of Isbi-Erra, the king, Sidu, a.k.a. Enlil-ibni, was scholar. During the reign of Abi-esuh, the king, Gimil-Gula and Taqis-Gula were the scholars. During the reign of [...], the king, Esagil-kin-apli was scholar. During the reign of Adad-apla-iddina, the king, Esagil-kin-ubba was scholar. During the reign of Nebuchadnezzar, the king, Esagil-kin-ubba was scholar. During the reign of Esarhaddon, the king, Aba-Enlil-dari was scholar, whom the Arameans call Ahiqar.

Not only did the Abgal gave wisdom and support to the king, but also provided wisdom to the people of Sumer. For example; Nungalpirigal made the bronze lyre according to the technique of Ninagal. The lyre was placed before Anu, the dwelling of his personal god. It is said that Oannes aka Uanna is said to have taught people the creation myth the Enuma Elis.
Now while there were only seven divine sages, there were also human appointed sages. These are not to be confused with the Abgal, though the ancient mythology classifies them as such.If you wish to learn more of these beings, then read these ancient literatures;Uruk List of Kings and Sages, Gilgamesh flood myth, Bit meseri, The Twenty-One "Poultices", The Poem of Erra, Berossus' Babyloniaca, etc.
sources: https://en.wikipedia.org/wiki/Apkallu, http://www.godchecker.com/pantheon/mesopotamian-mythology.php?deity=ABGAL


The second variation of the Abgal is Arabian Mythology. This deity is classified as a Jinn. Originating in the Palmyra region, the legends show him more of a young man, or a young warrior. It seemed that this warrior favored the bow and a lance while riding on a horse. Inscriptions say he was the god of nomads.
For more information read: The pantheon of Palmyra, by Teixidor, Javier (1979) and Cults and Beliefs and Edessa by Drijvers, H.J.W. (1980)
Source: https://en.wikipedia.org/wiki/Abgal_(god)#CITEREFTeixidor1979