Art by Roger Raupp

 This is a cover of Dragon magazine from 1987

https://rpggeek.com/rpgissue/64966/dragon-issue-125-sep-1987

Vol. XII No. 4 of Dragon Magazine.

Cover Art: As Camlann burns in the background, a wounded King Arthur prepares to meet the mounted attack of his hated rival Mordred. This painting was carefully researched by Roger Raupp, who based the weapons, armor, and fortifications on those in existence in the British Isles after A.D. 500. The battle shown here takes place at Hadrian's Wall, where some sources believe the historical Arthur lived. (from the contents page)

Wiki on Camlann and its historicity