For example: Illithids in and of themselves have a completely alien mindframe. While the basic goals may seem similar to any other villain (slaves, power, rule the world, etc.) their means and motivations are completely different. Mind flayers feel no positive emotions whatsoever, to the extent of not even understanding what positive emotions are. Happiness means nothing to them, because they have no understanding of it. Imagine this cold, clinical approach to a race that lives off human brains, and you'll have some truly frightening experiences.
This reminds me of something that I now want to put out.
I shall now provide tons of spoilers to the movie "The Forgotten" to make my point.
[sblock]The movie "The Forgotten" is about a mother who is told she "created" 8 years of memories of her son. It embarks her on a journey to find the truth when she discovers someone else suffering the same situation.
What's
really going on: aliens are running a test. They are observing the bond between a mother and her child. Because they are trying to understand love. To paraphrase one of the aliens: we can observe it, measure it, quantify it, but we don't know
how or
what it is.
Now, instead of aliens, replace Illithids, or Aboleth. Instead of "Love between mother and child", replace something else entirely. A whole adventure where the PCs are guinnea pigs inside a mental rat maze, for the illithid's understanding.
You really want to throw the PCs for a loop? At the end of an adventure, where they clearly destroy some illithid or something of that nature, at the beginning of next session, hand them new identities. They share similarities with their existing characters. Tell the PCs "Play this straight up." Now, insert dreams or flashes of the characters in a tank with something stuck to their scalp, over their chest, or glimpses of purple faced, white eyes peering down at them. Have it slowly wind down where the PCs "get" that something is amiss - they're not who they are, something like that, they destroy some sort of artifact - and they all simultaneously wake up inside pods with things attached to their scalps, inside the Illithid Mind Lab.[/sblock]
Something else I've been pondering recently: aberrations as bio-technology. Recently I was watching the first season of Babylon 5. In an episode, they discover bio-tech. Imagine a "sensor" created by recreating the tissue of several different species' sensory organs and programming that to give you data of some fashion. Or creating a data storage unit by replicating the neural pathways of the brain. Along with this was, naturally, a biological superweapon - it grafted itself onto a target, overrode him, and started growing armor and an organic energy weapon.
I could see this being reproduced with experimentation on aberrations.