Sentence:  I shivered and shook, and would have screqamed in my fright—but the Fiend,—as he seemed to be, —in a hoarse, croaking voice, charged me to keep silence,—saying that I had lain seven years bound for my sin, and that my soul would speedily be sent on an errand to sinners yet on the earth, to warn them from the evil of their ways, —and that, then, my punishment in Purgatory would be <WSD>alightened</WSD>. 
Meaning of the word marked with <WSD> tags:  To lighten; to reduce in weight or heaviness.