They knew there was something coming. It was hard to tell for sure back then, but as time passed, it grew increasingly clear. This... prediction? Vision? Would serve as the driving force behind their life's purpose, until their inevitable demise.
Even from birth, they knew what was to be done. Memories of a past life, and a vision of the incoming future; little time would be wasted from the moment they learned to speak. They spoke of unimaginable concepts, of fantastical creations, and of a society hardened and ready to face the threat nobody knew was even coming.
As they grew older, words and ideas became speeches and inventions. Where their predecessor failed, they came to succeed. What once was thought to be make-believe began to be realized. As their time drew to a close, the final pieces began to take shape.
I... am the last of my line. I carry the memories of not one, but two past lives within me, and this approaching doom that my past selves have spoken of for entire lifetimes is almost here. Society is ready.
The rest is all on me now.