It is associated with the sephira of Binah.
Abilities and function
In the hierarchy of angels, Zaphkiel is chief of the order of thrones and one of the 9 angels that rule Heaven; also one of the 7 archangels. He can watch people when they need to make important decisions and when they need to put them into words for others. If they are unsure of the words, he will help them to make the message more clear. The leader of the Erelim, he is associated with the planet Saturn.
The Grimoire of Armadel says that Zaphkiel teaches the functions and abilities of the fallen angels while they were still in Heaven. He also can tell the magician information about the fallen angels such as their places of habitation and how they were created.
According to Johann Georg Faust, Zaphkiel appears on Saturday morning at 1am, 3am, and 8am, then again in the night at 9pm and 12pm. He is in a human form surrounded by many other spirits. Its magical image is "A man like brilliant bronze, clothed in a Robe of white linen, holding an Inkstand in his hand."
Conflation with other angels
The conflation of Zaphkiel with Cassiel is explained by a mistranslation of the German grimoire of Johann Georg Faust. In his Magia naturalis et innaturalis (Magic Natural and Unnatural), Faust explains that Zaphkiel appears only on Saturday; however, in the context of the full passage, he is saying that Zaphkiel is the ruler over Barbiel in his capacity as the Archangel of Scorpio.