Enkidu is known to be Gilgamesh's only true friend. Much like Gilgamesh, it regards their friendship highly. While it currently has a humanoid form, it is not a human but is actually a living mud creature sculpted by the gods of the ancient past. Enkidu is neither male nor female, merely a monster made of clay that descended onto the earth and appeared in the forest.

It seems to greatly appreciate nature, and it finds it a relief that the world is still beautiful even after being covered by cities like Uruk. Enkidu is happy to sit while its Master is resting and simply allow itself to enjoy the magnificent natural landscape and the "song of the river." Even when dealing with the person who hurt its Master, it speaks serenely in a polite manner.

Enkidu's might is far beyond human comprehension, and Gilgamesh considers it to be his only equal in the world. It has a connection with nature, and it can speak in an animal language (獣の言葉) that allows it to understand, communicate with, and translate the "words" of its Master and other animals.

(Source: Type-Moon Wiki)