What is "guilefull"

Usage examples of "guilefull".

And sooth, men say that he was not the sonneOf mortall Syre, or other liuing wight,But wondrously begotten, and begonneBy false illusion of a guilefull Spright,On a faire Ladie Nonne, that whilome hightMatilda, daughter to Pubidius,Who was the Lord of Mathrauall by right,And coosen vnto king Ambrosius:Whence he indued was with skill so maruellous.