Chose the origin square - it may be any occupied square in range of the Hero.
The Hero needs line of sight to the square.
You cannot target an empty square.
The square of origin and every square within range 1 of this square, is affected. The affected squares need to have line of sight to the square of origin.
The cone attack originates from a square adjacent to the attacker in any of the orthogonal directions.
The Hero needs to have line of sight to the square of origin.
The cone is drawn as a cone, with its top originating in the square of origin. Following the cone's direction for each additional range, add one square to each side of the triangle.
The height of the cone is always 6 squares.
The line of sight is calculated from the Hero unless the attack is done through slit.
Observe that figures does not block line of sight for a cone attack.