I'll be honest, I'm going for as obvious of an Evil Dark Lord as I can here. Got my evil tower, my evil armies. Only problem is, I'm not an evil person. I dont want to destroy anything. The people here seem to have a talent for bringing out the light in something, so maybe they can bring me back from the darkness I've fallen into and I can fight to help keep the world alive.
The Deceiver, practical application.
Spy, blending into a society seems easier than trying to fight it.
The Great Palace, simply make one person out to be a figurehead in the palace that rivals the king's love and admiration. Build rumors around an attempt to overthrow the king to put the entire kingdom at edge. Always work in the background, let them fight among themselves. When they are distracted, possibly even at war with one another I will slip among the ranks and behead the king myself and lay claim to the land to bring it ruin.
Oh what a joy it will be to have my cult slowly undermine her regime gaining more and more power until at last a war will start and I will appear to rid all of them of there souls, absorbing this pathetic queen last. Forcing her to watch in terror as I absorb not only the souls of her strongest champions, but also the souls of my own followers and the life of all beings in this "perfect land", until at last she is the only living being left. Then when her will crumbles will I take her soul leaving only decaying corpse behind on a barren war torn waste land.
That or i could just steal everyone's virginity via tentacle rape.
I'll hunt down and corrupt the maidens, turning their powers against their fellows, creating a council of concubines who can turn any enemy i deem worth it into my followers, and with the theft power, even those not really worth it will fall under my sway effortlessly. As a dragon i would assume the form of a dragon who i (and many of you) know well. The crystals of my corruption will swallow the world, before my crystal harem and i leave it behind to shatter, and on to greater conquests.
couldn't be more of a curb stomp really. medieval weapons will have no effect plus im to big for a human to hurt me anyway. turn everyone into skeletal minions after my flame melts the flesh off their bones. might even just take Home for the challange. not that it really that would be that hard anyway. just follow the Endbringer tactic with mixed certainty and uncertainty to throw the worlds economy completely off the rails. destroy big cities fast and let the military then try to handle the theft minions. eventually civilization will try to survive in isolated pokets and then? a few decisive victories away from the end of the human race.