You need to identify the characteristics so that it is easier for you to hunt them, (if they aren't endangered). You would have better experience between all of this and it would just be simple for you. :)
The main idea of the passage above from Cotton Mather's "The Wonders of the Invisible World" is to justify the outcome of the trials. Thank you for posting your question. I hope this answer helped you. Let me know if you need more help.
Oh my gosh, I love the Harry Potter series. But anyways, the central idea of this paragraph is that Harry should be getting some rest for the ongiong match and Mrs. Weasley will get Harry and the other's supplies.