Solas is linked with Stolas in Joseph H. Peterson’s comparison of Goetic spirit names.
The spelling and catalogue account
Page 3 records “Solas or Stolas” in the Waite column and Solas in the Shah column. The connection follows this modern editorial comparison.
Weyer’s Pseudomonarchia Daemonum, section 69, names Stolas as a great prince appearing as a night-raven and then in human form. The entry associates the spirit with astronomy and knowledge of herbs and precious stones, and assigns twenty-six legions.
Sources
Peterson’s spelling comparison, page 3, and Pseudomonarchia Daemonum, section 69.