This question also has an answer here (in German):
"Es" in "Es ist gutes Wetter" However, that answer is in German, and clearly, my grasp of German is not sufficient to understand a nuianced answer.
I came across this sentence in a Ersteleser version of Die Schatzinsel:
Es waren seltsame, manchmal auch unheimliche Kerle darunter.
I can't reconcile "Es" with "waren". Or, if "waren" refers to "die Kerle", what role is "Es" playing?
The general meaning seems to be "It was weird, sometimes strange guys would come by." (refering to the "Gasthaus").