Invisibility spell

[Fred1]

I don't understand the behavior of Invisibility. Every time I cast it, I feel like it's a hit or miss. Sometimes my enemies see me, sometimes not. I got so paranoid that I wasn't sure if any sort of light source, like a torch or the Light spell, was affecting the spell. I then started to cast Darkness every time I wanted to use Invisibility, but to my surprise, the Air Elementals can see right through my magic, no matter how hard I try to hide from them.

So, how exactly does this spell work? Do I need to shut off my light source? Are there specific enemies that can easily see through my invisibility (Air Elementals are one of them, but I'm not sure if this is intended behaviour)?

EDIT: I'm aware that the invisibility is lost after attacking.

[Ichthyic]

enemies will see you if they are within one space of you, no matter what.

elementals can see you regardless.

some bosses (not all) can see you regardless.

otherwise, seems to work pretty well. even works on the leprechaun.

[Fred1]

enemies will see you if they are within one space of you, no matter what.

elementals can see you regardless.

some bosses (not all) can see you regardless.

otherwise, seems to work pretty well. even works on the leprechaun.

Hm, this makes sense. Thanks.

[minmay]

enemies will see you if they are within one space of you, no matter what.

From my observation it doesn't seem like this is actually true, although it definitely makes them more likely to take notice of you.
As long as you keep moving at least a little bit, invisibility pretty much makes you invincible from anything without see invisible, and very few monsters have see invisible. It's nuts even without backstabbing.