For his noble intentions he now fears Hamlet will take his life when he has the chance and receives what he deserves in the outcome of his ignoble acts. Not only does Claudius use deception to for his selfish reasons but he uses others to help in this treacherous act for the betterment of himself. He uses Rosencrantz and Guildenstern, Hamlets long time friends, to escort him to England where he will meet his death unknowingly. Claudius wants them to find the truth whether Hamlet is plotting to avenge his father and kill the king. This maneuver was laid out by Claudius in fear for his life and position on throne so he decides to get rid of Hamlet for good.
Guildenstern: "Which dreams indeed are ambition; for the very substance of the ambitious is merely the shadow of a dream. " (1.5.257-259) Rosencrantz: "Truly, and I hold ambition of so airy and light a quality that it is but a shadow's shadow. " (1.5.261-262).
Since Rosencrantz and Guildenstern are Hamlet's old friends, Claudius thinks Hamlet might reveal his ideas to them before he is put to death. This is why the two speak of "ambition" when they talk to Hamlet. If a Prince is ambitious there's only one step up for him, and that's to become King. Since it was Rosencrantz and Guildenstern's wrongdoing for going along with the plan of Claudius' and also their inability to perceive the deception portrayed by Hamlet, they ultimately faced the consequences with their deaths. Finally, Claudius sets up a fencing duel between Hamlet and Laertes noting that it is to determine who has greater love for Ophelia. As that was told to Hamlet, Laertes was told it was to get revenge for killing Polonius therefore the tip of the sword will have been sharpened with the venom of a snake on it as a result only one knick would determine the fate of Hamlet: "Revenge should have no bounds. But, good Laertes,/ Will you do this, keep close within your chamber.