I dreamt my lady came and found me dead—
Strange dream, that gives a dead man leave to think—
And breathed such life with kisses in my lips
That I revived and was an emperor.
Ah me! How sweet is love itself possessed
When but love’s shadows are so rich in joy!

In exile in Mantua, and before learning from Balthasar that Juliet is "dead," Romeo describes in Act 5, Scene 1 a “strange dream” in which he himself has died. However, Juliet’s kiss brings him back to life. Romeo adds that it would be wonderful if he and his love could actually be together again, since just dreaming about Juliet fills him with joy.

Then I defy you, stars!

In Act 5, Scene 1, when Balthasar reveals Juliet’s (apparent) death, Romeo erupts with this quote decrying fate. He believes it has been particularly cruel to him and Juliet. Read more about this quote in Quotes by Theme: The Inevitability of Fate (the fourth quote) as well as in Quotes by Character: Romeo (eighth quote).

Such mortal drugs I have, but Mantua’s law
Is death to any he that utters them

To buy the poison with which he intends to commit suicide, Romeo in Act 5, Scene 1 seeks out a Mantua apothecary. An apothecary is a seller and dispenser of drugs, much like a pharmacist in the present day. When Romeo asks him for a poison (which is illegal), the Apothecary refuses, pointing out that selling banned drugs is punishable by death. Seeing how poor the Apothecary is, Romeo offers to pay him handsomely for the illegal transaction.

There is thy gold, worse poison to men’s souls,
Doing more murder in this loathsome world,
Than these poor compounds that thou mayst not sell.
I sell thee poison. Thou hast sold me none.

Romeo, who we have seen previously being quite persuasive, makes an appeal to the Apothecary using a clever argument. In essence, what he is saying is this: "I’ll give you gold for the illegal drug, and since money is a worse influence on society than drugs, it’s basically me who is committing the crime of dispensing poison, not you." Either because of a combination of the gold and the argument or just the gold alone, the Apothecary complies with Romeo’s request and sells him the poison. Read more about this quote in Quotes by Symbol: Poison (the third quote).