Gwent: The Witcher Card Game
Choose a unit. If it's boosted, damage it by double the amount boosted. If it's damaged, boost it by double the amount damaged.
See this subject on The Witcher wiki: Jan Bekker
Gwent Update: Oct 23, 2018: Ability Rework. Removed Special tag. Now Gold (was Silver).
Gwent Update: Feb 09, 2018: Name change: Bekker's Dark Mirror (was Twisted Mirror).
Gwent Update: Dec 19, 2017: Name change: Twisted Mirror (was Bekker's Twisted Mirror).
Gwent Update: Aug 29, 2017: Capped the ability at 20 power. Added Spell tag.
Gwent Update: May 24, 2017: Doesn't affect gold cards anymore. Now Silver (was Gold).
Gwent Update: Dec 19, 2016: Added.