tomorrows book

A relic of the past. From when dragons were on earth. She was the best, an immortal archmage, titled Keeper of Secrets. One who holds all the knowledge in the world. When reality shifts, taking away all the mana in the world. They start dying until only she was left. She casts a spell known as hibernation but modified it to use her own mana. The condition to end the spell is when mana is felt.