You can find the main JS scripts used by the theme in the folder Assets/js.
Narratium use AngularJS through the entire theme. Main-app.js is the angularjs application used to manage the various js features related with AngularJS through the theme. This app is called in the body element of the layout.
The AngularJS code necessary to active this library in the theme is defined in theme-features/site-angularjs.php.
The vast majority of the files in Assets/js are related with the AngularJS app. Others scripts used in separated features of the theme can be founded in its respective directories.
This hook is declared in the function KTT_add_angularjs_app in theme-features/site-angularjs/site-angularjs.php. This function displays the angularJS main app in the footer of the site and thanks to the action hook THEME_angularjs_main_app declared in it, others separate features can inject code in the main app.