Anonymous
Do you know of any unique/ancient sigils/symbols used for warding off evil/demons?

actually, ironically I do.

I, myself, use a technique found in the Simon Necronomicon.
http://www.lovecraft.ru/texts/necro/simon_eng/names50.html

      

The simplest ward in the world (at least to me) is to recite the word BANRABISHU (facing each direction, north, south, east, west) and the repeating with BANMASKIM. I know it sounds corny, but it has worked for me for years. As with anything metaphysical, the more energy you devote towards it, the better the results.