I was given a theme called Orion available from themeforest. I had experienced troubles installing it via GUI (style.css was missing), therefore I did that operation manually by copying Update directory up the directory tree.
Now the theme appears somehow empty/broken. I was wondering whether this specific theme is meant to be standalone or just as an update to a prerequired theme (and which one, if this is the case).
Edit: I apologize as I wasn't clear enough. Is it normal that the theme .zip file which should be used to install the theme does not contain style.css? Why is the stylesheet only included in Update folder and what is (usually) the purpose of that subfolder?