The phrase "dampening spirits" refers to something that has a depressing or disheartening effect on someone. There are a number of words which could be considered antonyms for this phrase, including "invigorating," "uplifting," and "inspirational." Something that is invigorating would have the opposite effect of dampening spirits, making someone feel energized and excited. Similarly, something that is uplifting would be a welcome dose of positivity, while something that is inspirational could serve as a source of motivation and encouragement. These antonyms can help to evoke the opposite feeling in someone and lift their spirits, serving as a powerful antidote to anything that might otherwise dampen them.