Back in Westeros, ten years of tonics and potions for strength and stamina plus mere age began to take a toll on the now 70 year old King. No matter what any Maester, healer or woman did, he was lucky to get a single erection per day and with less than half of those he was actually able to come.
He had also developed a severe and rapidly spreading case of arthritis that had begun in his fingers but had quickly gone to his wrists, elbows, shoulders followed by knees, hips and ankles. Within a year of the first signs manifesting, both hands were warped into something resembling claws and within only two years of the initial onset, Viserys was completely crippled. Most days, he suffered from debilitating pain in nearly every joint as the inflammation was so severe. Maesters and healers tried everything they could to reduce the inflammation and ease the King's pain to no avail. It didn't take long for the once rather plump King to look nearly skeletal.
The arthritis wasn't the King's only malady either. By age 65, Viserys had become a haunted man. He would see Aemma's gutted body covered in blood on his bed and table and her corpse masking the faces and bodies of his women when he fucked them. He would see the tear streaked face of his 12 year old daughter begging him to listen to her in the Throne room and in his chambers. He would see Daemon accusing him of surrounding himself with vipers before while dressed in full Valyrian Steel dragon armor. He would see his father and grandsire's looks of pure disappointment following him everywhere he went and his cousin Rhaenys shaking her head at him.
His dreams weren't left alone either. At age 72, he began to have dreams that tormented him. They were filled with his grandparents' rage at what a failure of a King, father, husband and brother he was. His grandsire admitted to not having been a very good father, but at least he was remembered as a good King. Viserys, however, was a kinslayer and a failure in every way.
Viserys was also visited in his dreams by his parents, Uncle Aemon, Aunt Jocelyn, Aunt Daella and Uncle Roderick. His parents absolutely disowned him and loved to rage at him for all of his many failings. They showed him glimpses into his brother's life, home and family.
His Uncle Aemon and Aunt Jocelyn also raged at his terrible choices and everything he had done and how poorly he had used their daughter and her family.
As for his Aunt Daella and Uncle Roderick, they both had much to say about his abysmal treatment of their only daughter and their granddaughter. They both spoke of their pride in everything their granddaughter had achieved in her life and how much of a devoted wife, mother and grandmother she was. They also shared with him glimpses of his daughter's life from the time she left Westeros to the present date. These dreams always left Viserys in tears as he knew that there was no way he could travel to see his daughter again and meet her youngest children and her grandchildren.
Aemma was also not a stranger in his dreams. He got to experience from her point of view the first time he fucked her as a 21 year old Prince and she a young maiden of a mere 9 years. He also got to experience every miscarriage and every birth and even every time he fucked her still healing body following each one. He never knew just how much pain he had truly inflicted upon his beloved Aemma through all of that. However, what was worse was when he dreamt of her final birth. He was trapped in her body as he ordered her held down even while she was wracked with agonizing contractions and as the blade was driven into her body, slicing her open sternum to cunt. He felt every bit of each contraction, her feelings of betrayal once she realized what was going to happen to her on his orders and her fears for their still young daughter before the cold steel split her belly in two and ended her life. He realized that his wife's last thoughts were not on him, the pain or their son but on her precious little girl and only living child and how she wished she could say goodbye to her. He got to relive Aemma's living nightmare over and over at least once per week, every single week, even as it drove him closer and closer to the point of absolute madness.
In addition to all of this, the Gods' sent Viserys dreams of the future of Westeros. The decades of civil war. The return of the Night King. The millions of innocent lives lost. They showed him history books that lay all the blame for the downfall of the Seven Kingdoms squarely on his shoulders as he betrayed his house and Gods. He was shown foreign powers sweeping in and conquering different parts of Westeros. Danes conquering the Westerlands, Riverlands and Iron Islands where they would rule for centuries. The Vale being conquered first by Pentos and then other nation states. The Crownlands eventually coming under the rule of an ambitious Dothraki warlord. Dorne taking over the Stepstones and the Reach while the Stormlands eventually fell to the Triarchy. Only the North remained an unbroken and unconquered Kingdom though they would ally with the Danes. Viserys would also see the rise of the dragons of Essos and how, even centuries later, they rejected all opportunities to conquer Westeros showing Viserys just how much his brother truly had not wanted his throne.
Nothing the Maesters and healers gave him was able to help him escape the dreams or his hauntings either and no one knew what to do. All they knew was that their monarch was slowly being driven mad even as his body gave him ever increasing amounts of pain and deformity.
Religious leaders from all over were summoned to aid the King by his council and they tried endless prayers, rituals and even a couple different forms of exorcisms but nothing worked to make the King improve. If anything, the treatments just made everything worse.