def control_char_symbol(c: str) -> str:
    """Returns one of the Unicode Control Picture characters (e.g. '␛') for
    the given single-character string with an ord() less than 32.

    Raises ValueError for invalid strings.
    """
    if len(c) != 1 or ord(c) >= 32:
        raise ValueError('Argument must be a single-character string with an ord() < 32')

    return chr(ord('␀') + ord(c))