Energy » Aurora Energy
The discard cost on Aurora Energy only applies when attaching the card from your hand. If you attach it from somewhere else, you don't have to discard a card from your hand.
Source: Sword & Shield FAQ (2020-01-24), TPCi Rules Team (2020-02-06)

Relevant cards

Note: All applicable cards may not be listed below.
SWSH1_186
SWSH1_186