"Our Prophets are false! Open your eyes, my brothers! They would use the faith of our forefathers to bring ruin to us all! The Great Journey is a-"- Sesa 'Refumee's hologram being cut off by the Prophet of Truth.
"Deal with him, my brothers! I will defend the Oracle. His truth must not be silenced!"- In the level The Arbiter.
"I wondered who the Prophets would send to silence me. An Arbiter?... I'm flattered."- Sesa 'Refumee's hologram in the level The Oracle.
"This will save me from the storm, but you will be consumed."- To the Arbiter, behind the shielded door.
"Arbiter. I would rather die by your hands than let the Prophets lead me to slaughter."- Sesa. He is saying that he would rather have a high ranking, honorable brother (Elite) have to kill him instead of having the Prophets kill everyone including him with the Great Journey.
"Ask the Oracle about Halo. How they would sacrifice us all for nothing!"- To the Arbiter.
"The Elites are blind, Arbiter! But I will make them see..."- While activating two holo-drones.
"How did the Prophets buy your loyalty, Arbiter? With a new command, a new fleet, ... or was it the promise ... their "Great Journey?"
"Look around you, Arbiter. This facility and dozens like it devoted in the study of the Parasite, but where are the weapons, Arbiter?! What was the result?! All that time and effort and the best the Forerunners could do was put these foul creatures on ice."
"And now where are these "gods" the Prophets would have us worship! Transcended? Ha ha ha ha ha! Hardly. Come, Arbiter, let me show you where they went."
"I see the Prophets have chosen poorly, Arbiter!"- If you missed him with your shot.
"I take no pleasure in spilling a brother's blood."- If he kills the Arbiter, or during combat. Sesa is showing that he does not want to kill the Arbiter or any one of the Covenant, quite the opposite, but if they can't see and understand what the Great Journey really is then he must kill them.
"That will send a message to the Prophets."- If he kills the Arbiter.
"Come Oracle, we have much to do."- If he kills the Arbiter.
"I'll give you a moment's rest, and then we begin again."- If the Arbiter takes cover, hides or activates active camouflage.