Sentence:  But he by wild and way ... / Rode till the star above the wakening sun, / Beside that tower where Percivale was <WSD>cowl'd</WSD> ["i.e." became a monk], / Glanced from the rosy forehead of the dawn. 
Meaning of the word marked with <WSD> tags:  To cover with, or as if with, a cowl (hood).