Romeo calls it a cordial because, the poison will "help heal his heart".
Also cordial means <span>a comforting or pleasant-tasting medicine. So in a sense it is helping him heal, so he can be with Juliet.</span>
He suffers complete ruin and death
The mood is unsettling and suspenseful. The words "unfamiliar, concerned, unusually, and heavy" help set the mood to this.
