haaaa sur ce coup là... l'ultimate guide donne le penetrating comme un extra pour le pouvoir :
Penetrating: Normally, the hardness of the ground affects
only the speed at which you burrow. At the GM’s discretion,
some super-hard materials may be considered Impervious to
Burrowing, in which case this extra allows you to dig through
them, provided your Penetrating rank reduces the material’s
Impervious Toughness to equal to your less than your Burrowing
rank.
