Like most Imps, he is a diminutive humanoid of incredibly short stature with an animal-like head, in his case having the head of a hawk. His attire appears to be Egyptian in nature.
When he temporarily became The Sultan's minister of war, he was given a new set of regal clothing befitting his brief rise in power.
As his name implies, Nefir has an insatiable greed (hence Nefir Hasenuf which is similar to Never has Enough) which can never be satisfied no matter how much gold he has. He is willing to do anything to earn money, even if it means endangering people's lives, scamming people, or outright starting wars that could kill people just to earn money. He usually doesn't like to get his hands dirty, as evident in each of his appearances where he always orders his minions to build stuff rather than do the work himself. He even mentions in "Mission Imp: Possible" that he doesn't do manual labor but instead supervises. In "The Way We War", he states he hates violence but loves detailed accounts of it, further showing he hates getting his hands dirty but loves causing others suffering.
His first appearance is in the episode Never Say Nefir. He was fixing the buildings of Getzistan when Samir the Destroyer began destroying Getzistan daily. Sultan Pasta al Dente was at a loss for the destruction and hired the Imps. Nefir introduced himself to Aladdin and his friends when they arrived but was quick to point out Genie's human disguise as fake, and was disgusted at the fact that a Genie was around. Later, when Aladdin inadvertently volunteered to get rid of Samir, Nefir was devastated as that would cause a loss in profits. Genie, Aladdin and the others tried to get rid of Samir but failed. The next day Genie tried to build a rocket to prepare for Samir's return, but Nefir and his Imps sabotaged it.
He tricks Genie into helping him steal golden thread from Mothias, the natural enemy of Imps by posioning Aladdin with a sleeping drink that can only be cured by the golden thread of Mothias.
He stages a war between Odiferous and Agrabah by stealing the Odiferons' sacred crock of cheese and claiming that Agrabah was the one who stole it. He sold weapons to both sides but Aladdin discovered his treachery and both kingdoms demanded a return along with him and his Imps repairing everything. His fate afterwards remains unknown.