Phoenix is a great marquis in Johann Weyer’s Pseudomonarchia Daemonum.
Bird form, sciences and poetry
Section 68 describes Phoenix appearing in the form of the fabulous bird, with a child’s voice and a sweet song. In human form, the spirit is said to speak about the sciences. The catalogue also describes an excellent poet and assigns Phoenix twenty legions.
Source
Pseudomonarchia Daemonum, section 68, Joseph H. Peterson’s digital edition presenting Weyer’s Latin and Reginald Scot’s English text.