Rhaegar had been woken by the Lord of Light and he should have considered it a gift. He had every opportunity to help his siblings and his one remaining child, but as he roamed the lands for seventeen years, he dealt with the mourning of all the blood spilled during the Rebellion, including of those he loved most dearly. He also felt the pain of his wounds that had originally taken his life. Whenever he moved, he could sense his ribs aching from the crack of Robert's great hammer. They had the tension and flare up of what would be broken bones and torn muscle. He would bend over, hugging his chest as he felt the spear that stopped his heart again and again. It was sharp and sent shock waves through his body. His face always felt swollen and torn from the hammer again, but when he put a hand to his cheek, he felt scars and the rest was a flat surface. He was carrying with him the duel that had been his great mistake. Walking into the water was his undoing. Slipping was the chance his enemy needed and now the Lord of Light kept sending him reminders of his fall. They would stall him. The undead dragon would be forced to hide and wail over the physical torture he was being put through.
Then the emotional pain would seep in. He was gifted with visions in flames. Rhaegar could watch as his children were murdered brutally and then Elia scream for her brother as she was attacked by the Mountain in the most cruel fashion. Tears would stream down his face and as he reached into the fire, the vision would wave and distort before returning to being crystal clear. The dragon couldn't help or comfort his wife. All he could was watch and then came Lyanna. Her agony while trying to give birth with little help, in the tower. She was without him and feeling alone as the child came into the world. She bled out and he watched as Ned came running in to take the child as his sister breathed her last breaths. Rhaegar would hide his face in his hands and want to rip his heart from his chest, so maybe he wouldn't feel the despair. The last vision was of his brother continually punishing his sister for the death of their mother and abusing her without a care. She had little worth to him. He never valued women other than their Queen mother. Madness was sinking into Viserys and the horror of it was too much for the eldest to stand. He began to stop making fires and shivered in the cold, preferring the frigged air over the visions. His mind was churning.
As life continued, Rhaegar began to become more twitchy and far deeper in darkness. He started to burn things to see events unfolding. He witnessed his sister being sold off and her being treated like a slave. Then he witnessed, while burning a random peasant's home, the death of their brother and the scream echoed through his mind. He couldn't get passed the pathetic cries and it made the wounds spike in misery again. After a little while passed, he burned a tavern to see the death of Khal Drogo and the hatching of Daenerys' dragons. He stood in wonder as the people who had been inside the establishment ran out in terror. He was in awe of what his baby sister was becoming. When he finally noticed the customers fleeing for his lives, he realized he was disconnecting. His ribs began to feel like they were breaking again and he bent over, groaning next to the flames. "Keep seeking the build", the Lord of Light spoke from the flames. Rhaegar looked up to see Sansa Stark being beaten and realized he was only checking on his family. Not Lyanna's. He titled his head at the new boy king and saw his father's insanity in him. He went numb. Death was coming for them all.
Rhaegar went from port to port until he found one ship worth boarding and another worth burning. He set it to flame and saw the Sand Snakes training for battle as Oberyn watched. The Martells remained bitter, but strong. This was the only good thing the undead dragon had seen in his visions. Quickly it shifted to the armies led by Rob Stark.
Rhaegar had heard the news of Ned Stark's death and knew the Lannisters now ruled. He remembered how awful they had been from the beginning. Always plotting and they were the reason his family was dead. Rob didn't stand a chance. His lack of pity was not fitting to the personality he once had. He was losing a piece of himself. He was starting to lose compassion for what he perceived as small events. He knew bigger things were coming, but he believed in them before his death. Even then, he cared for the small moments and individuals. Now he only cared about the Night King and the long night. He thought everything else was a waste. He boarded a ship to find his sister. He was compelled to bring her into the mix and point her dragons north rather than have her fix her eyes on King's Landing. When he boarded, many passengers chose to leave. His eyes went from deep violet to red flame. He was something that unsettled the people of Westeros. He was a creation of the Lord of Light.