Can I use Hisuian Samurott's "Wily Stance" Ability if there are no cards in my deck, just to discard an Energy?
No, you cannot.
Wily Stance




x2Wily Stance
You must discard a card from your hand in order to use this Ability. Once during your turn, you may draw 3 cards.


Dark MasteryThis attack does 20 more damage for each Energy attached to all of your Pokémon.
Hard of heart and deft of blade, this rare form of Samurott is a product of the Pokémon’s evolution in the region of Hisui. Its turbulent blows crash into foes like ceaseless pounding waves.
Can I use Hisuian Samurott's "Wily Stance" Ability if there are no cards in my deck, just to discard an Energy?
No, you cannot.