Don’t use quotes around a term just because sometimes people say it (or whatever the usual excuse is for using quotation marks around things that don’t need ’em). For this example, get rid of the quotation marks around devil’s eyes.
I added and after devil’s eyes because that was the least invasive way to fix that part of the sentence.
The writer may not have intended it this way, but I do like how the wording of the first sentence implies black magic and witchcraft are different things.
You need a comma before is because everything after killer and before is is nonrestrictive. (You could just write This dangerous killer is said to look and smell like death, and although that sentence would be less informative, it would be complete.)
*sigh* Sometimes it’s too much effort to explain all the changes… Just look at the corrected version, okay?
This dangerous killer, sometimes known as devil’s eyes and once used in black magic and witchcraft, is said to look and smell like death. Smelling the toxic leaves causes symptoms of dizziness, stupor, insanity, dry mouth, dilated pupils, restlessness, hallucinations, and delirium leading to a coma and ultimately death.
Now it’s still a bit clunky and awkward, but at least it’s punctuated correctly. 🙂
(It should be noted that, unlike stellar radiation and other things of a non-chemical lethality, plant leaves can properly be described as toxic.)