So I love a bit of exploring areas I’m not necessarily meant to be in, but broke the end of act 2 a little bit.
Went down the stairs in moonrise towers before fighting Ketheric on the roof and found myself in the mind flayers den with the blood lake where you can hear chop in the butchery, but can’t reach him.
Turns out you can.
Either misty step or dimension door can be successfully cast to get you into the butchery, which if you proceed gives you no way back and lands you on a path to the final Ketheric fight without having faced him on the roof.
Not a great glitch or anything but thought it worth sharing none the less.
While true, if you’re just looking to steal something once you probably have to roll a 1 to become revealed.
If you want to get deep into the shenanigans, have someone cast Pass Without A Trace on your character before you apply Greater Invis (with someone else, since both are Concentration) and make sure your sneak thief has advantage on Stealth checks from somewhere (there is a Leather Armor that grants this for example).
You can probably kill off a couple of enemies in a group before breaking Invis (and thus never entering combat) with that setup, especially if you also have Expertise.