This is a letter written to Gilbert before the end of seed by Rau. We really didn't see a clear path as to gilberts reasons for doing what he did nor why he had ray try to follow Rau's path. Perhaps this will explain it a bit, enjoy of course comment please.
Thoughts of a mad man
How cruel this world truly is, I have seen these depths or rather these mere glimpse into the hell we have created to ourselves. Oh yes my dear friend we can not escape the hell not only that we create for our selves but the hell humanity has created for us all. While we may escape our own personal hell we will find just beyond the final door yet another hell created by the wickedness and utter evil of our own ambitions.
My own life, my very existence is a direct result of this ambition. My fathers lust for eternal life how pathetic an man he was. However he is not alone in this sin there were many many more. The result was the creation of that boy. A creation I did not think survived how wondrously cruel fate is. That abomination by the name of kira. Yet this is a sin even you share.
I have learned that he is key however to opening the final door…..at least my own final door out of this half hearted creation known as life. However should I fail to take him with me he will inevitably be the door shielding humanity from there well deserved fate. To remove this door you must use the right key a very special key I didn't even knew I had till it was too late. The key to kira yamato is his friend our very own Athrun Zala. If you get to athrun and can control him you can control and kill kira, thus removing the door.
Ah my friend I can see the look on your face as you read this. That somber disappointing scowl. I wonder do you now regret creating the pills that have kept me alive? Do you judge me as insane? Ah yes I can actually hear your thoughts, was it the pills? Was it the position I put him in? could I have prevented this?. The answer is irrelevant you can not change the past, but you can change the future.
Yes you can change the future, our destiny is in your hands now. This is a burden I was hoping I could carry alone. I seriously doubt I can do it alone now, thus I must entrust our destiny to you. Although I will be gone I leave you two bits help one are the very pills that gave my physical life have also given me eternal life my own hell if you will. Take the pills and play some chess and we shall see and speak again. Last I leave you ray or should I say I leave you me. Use him as you see the need to, he will understand after all I am him and he is me.
Gilbert take over this plan, this destiny plan. As one last favor and request.
I will see you again soon
Rau