Does it counts a luggage? Can it be traded?
How to lose it?
It does not count as luggage, can not be traded and you can not lose it. It does not count as an object.
After I read over the rule book, I consider: When odd number players, the victory items of inferior team become 2 keies or goblets? And every player can proclaim the victory? (Everyone owns this card.)
You are right: The "drink of power" is in fact a "rulecard" that says that the inferior (outnumbered) team can win with 2 goblets/keys. That's all. You are not allowed to proclaim the victory with the "drink of power". You also need at least one key/goblet to proclaim the victory.