It's all about flat chests and robes over robes over robes.
I'm pretty odd aren't I?
I like robes too. Really pretty, fancy, well-designed robes and clothing. Especially big, flowy ones that trail behind you and have those beautiful long sleeves. Gems and obscuring hood makes them even prettier and more mysterious. It isn't really something sexual to me, but it just looks beautiful and cool. Fire Emblem has some gorgeous robes for the character portraits and the sprites. Summoner and Druid robes are especially awesome.
Another something I really like in a not-sexual way are masks. Especially those featureless, evil masks or cool comedy and tragedy masks. They just scream 'mysterious and badass'. Even better if they have a nice design or cool engravings and symbols. Helmets with a similar design to these masks also appeal to me. A mask is especially perfect if it doesn't have a mouth or other such features, only showing sinister, glowing eyes. This is one of the reasons why I like Dimentio so much. Its all about the masks, baby~
Because of this almost all the 'final bossy' monsters I draw have sinister, featureless mask faces. I just can't get enough of them.