>the villain's motivations are insane/incomprehensible

As in make it explainable? He's nuts, that's all the explanation you need

Now if you want to act in a lolrandom manner, just write down all the possible actions the guy could take and throw a dart at your list

>>51418931
Don't have it communicate ever with the players and make it follow odd but consistent rules.

>>51418955
As in, make it so that it's not awful.
It's only too easy to make a villain terrible by just giving them nonsensical motivations. Look at how hard it is to write the Joker.

Only about one time in a hundred is the Joker written well, and even then not for very long.

>>51418931

You get really really high, and then you roll with it.

I suggest priming minis with spraypaint cans in an enclosed space with poor ventilation before double fisting some strong drinks and then watching b movies and listening to 60's country ballads about the wild west (I suggest marty robbins) while writing campaign notes.

I guarantee that you'll get something incomprehensible, but strangely coherent.

Elder Gods/Eldrazi. They have reasons... mere mortals can't understand them, but they have them.

>>51418931
Someone on /v/ explained it pretty well when talking about the Reapers in Mass Effect.

Think of people as ants on your lawn. They are out there, foraging for food you dropped and using the soil you care for. Every so often, you mow the lawn and destroy everything they have. They cannot understand why or how you do this.

>>51418931
Villain is not the focus of the story.

File: loved one.jpg (73KB, 650x650px) Image search: [Google]

73KB, 650x650px

>>51418931
>insane

Give them a delusion. They act logically, from their perspective, but anyone else there's a clear disconnect between them and reality. These motives can be understood, because there is a form of logic there, but only if you happen to know the exact thing that distorts their view of the world. You might have a villain acting under the assumption that terrible crimes deserve death, but their definition of a "terrible crime" doesn't mesh with anyone but themselves. I once had a minor villain whose daughter died, and that built a mechanical copy of her. He'd convinced himself that she was still alive and reacted badly to things that threatened his delusion. As in, killing people trying to console him or get him out of his workshop. He'd do anything, as long as she was alive.

>incomprehensible
A force of nature that just does things, but no one knows why. I like to have more understandable villains whose goals involve unleashing the thing, but the thing itself has little to no characterization of its own.