Agiel is mentioned as a Spirit in such works as the Key of Solomon.
From Hebrew: אגיאל: The Intelligence (beneficial spirit) of Saturn. Association : Haniel, Elubeb, Asmodaï
Agiel is the presiding spirit of the planet Saturn, with Zazel.
As it says on the 10th Plate: "The First Pentacle of Mercury.--It serveth to invoke the Spirits who are under the Firmament.". And the letters forming the names of the Spirits Yekahel and Agiel. He is also described as protecting from deads.
The name of the spirit was written on a talisman that belonged to Catherine de Medicis, Queen of France.