How to hide meta box values from custom fields list?

Just add an underscore before the metabox ID so the part of your code where you add a metabox looks something like this:

$id             = '_drama-description';
$title="Description";
$callback       = 'drama_description_metabox_markup';
$screen         = $post_type;
$context="normal";
$priority       = 'high';
$callback_args="null";
add_meta_box($id, $title, $callback, $screen, $context, $priority, $callback_args);

You also need to replace every occurance of drama-description to _drama-description in the part where you save the data. Hope it helps.