How do Illithids act in society?

Through the Forgotten Realms wiki and Wikipedia entries on illthids/mind flayers, I’ve been able to gather the fact that Mind Flayers will usually never act alone, accompanied usually by 2 or more slaves. Also, mindflayer groups will go to take settlements.

However, when they are protecting the elder brain or travelling the Underdark, do they work in groups of 2 or more? Or will they tend to be alone along with their slaves?