Apkallu (aka Abgal to the Sumerians) were a type of divine being in Mesopotamian religion. The Apkallu were Seven Sages that pre-date the world flood (as seen in the Epic of Gilgamesh and the story of Noah) who were servants of the god Enki and sent to give humanity the ME (the set of moral codes, gifts, and laws ordained by the gods. Examples of ME include art, craftsmanship, law, prostitution, priests, and the destruction of cities, among a hundred other things).
Traditionally, antediluvian Apkallu are depicted in one of three ways: bird headed, human, and fish. The bird-headed variation is of a winged humanoid with the head of a raptor. While in reliefs they are depicted with two wings, in statuettes they tend to have four wings. The human variation is the same, sans bird head. The fish Apkallu are usually depicted as wingless men in cloaks made out of fish skins. Timeline-wise, the fish Apkallu came first and originated among the Babylonians, and the bird-headed idea came from the Assyrians, but then things got all cultural and wibbly-wobbly and everyone started to share.
Apkallu are often depicted holding either a bucket or a cone. The bucket (banduddû) is thought to be for holding holy water and used for healing, while the cone (mullilu) is a purification device. The Apkallu sprinkle the blessed water on the injured to heal them. Scholars are still trying to figure out what, exactly, the cone does, but the word mullilu literally translates into "cleaner," and these are holy beings, so we know it's something purification-related.
Mythologically, after the flood the Apkallu went to serve as advisers to seven different human kings, and eventually they pulled a grigori and hankied the panky with humans, leading to a generation of part-Apkallu part-human hybrids. The four Apkullu offspring then went on to be sages and advisers to royalty themselves.
The names of the seven sages are:
Uanna-Adapa apkallu
U'anduga apkallu
Enmeduga apkallu
En-megalamma apkallu
An-enlilda apkallu
En-mebulunga apkallu
Utuabzu-En-men-dur-ana apkallu
It should be known that Adapa is a legendary figure in his own right who ascended to become one ofthe Apkallu, and that scholars argue over which one of the Apkallu he is. Most say that Uanna is the ascended Adapa, while others say Utuabzu is him.
Apkallu are found in Assyrian art, mostly in the form of wall reliefs. They were considered to be guardians against evil, much like gargoyles on churches. They are often conflated with winged genies.