Willpower affects the radius of an alchemy explosion.
When a player 'a'plies the alchemy skill and chooses the wrong ingredients a fiery explosion engulfs the character.
The radius of this explosion increases with a high value in the Willpower attribute.
This gives a character with fire immunity and equipment protection items the ability to create unlimited large area of effect fire balls.
As even 2 herbs mixed results in an explosion and herbs are easy to acquire in large quantities.
Willpower should not affect the radius.
I would like to suggest that when 2 herbs are mixed, the resulting explosion only occurs on the tile the PC is occupying.