Lord Tywin knew that though such a power existed, he must keep it safe; the king would only spill over into madness if he could comprehend anything further.
He tasked Gerion to take the newborn dragon across the Narrow Sea, and Gerion soon understood the importance of his mission.
Lord Tywin could only carry on as if his wife had died which she had; and which in the form of a dragon could only reduce some of his pain, and his wife however somehow growing large enough to fight at his side reliant on the secrecy of his plan.
It was no difficulty, then, for all the hardness of his spirit to be enacted on the westerlands; to continue in his stead as Hand of the King; to continue as though Joanna truly was lost, for though her spirit was with him, her body and her mind was not.
As the years passed, he heard not from Gerion, and it was easier to let her go, and often times, he thought it better that she should; the hope was love, and to love was death, having now lost it and ruthlessly continuing on.
In the years that passed, the king grew suspicious and mad; he appointed Jaime to the Kingsguard, and so Lord Tywin took Cersei and resigned the Handship.
When Lord Tywin rode down the goldroad towards Casterly Rock, Cersei in a snit, and his men anxious that the king had been snubbed; Lord Tywin thought about the whispers from Varys about curious sightings across the Narrow Sea.
It bothered him that he had not heard from Gerion. But though every tool had a task; dragon or no, Lord Tywin would make sure the Mad King would pay.