I found a magnifying glass that belonged to Halaster in a room after a rather easy fight with *beeeep* [spoiler warning]
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a dragon on the first lvl. of the undermountain...what do I use the glass for?

You can use it to kill Formians easily. It might also have an effect on other insectoids, but Ive never bothered to check.

What the *beeep* are formian....Oooh...now I get it...thanx....I wonder...If I could use it in Neverwinter to eradicate those firebeetles