Viserys is the last surviving son of the Targaryen family after Robert Baratheon claimed the Iron Throne. Along with his sister, Daenerys, he lives in the land across the Narrow Sea.
Viserys is the second son of Aerys II and thus has a claim to be rightful heir to the Iron Throne. He and his sister Daenerys escaped from Westeros after Robert Baratheon led several other noble houses in rebellion against House Targaryen and seized the Iron Throne. Viserys, only a child at the time of the uprising, was forced to hide in poverty and exile with his sister. They have lived as the guests of Magister Illyrio Mopatis of Pentos for the past year. Viserys sees himself as the rightful King of the Seven Kingdoms and plans to return to claim it as his own.
In the first episode 'Winter is Coming', Viserys agrees to wed his sister to Khal Drogo in exchange for a Dothraki army to take back his throne. Daenerys is hesitant about marrying the Khal but Viserys forces her, telling her that going home with an army is the only way they can ever return to Westeros.
As time progresses Viserys becomes increasingly more frustrated at Khal Drogo's seeming lack of interest in providing the promised army. He takes his frustrations out on Daenerys. When he thinks Daenerys is ordering him in her new position as the Khaleesi, he assaults her and is nearly killed by Rakharo for it, before Daenerys orders Rakharo to stop. Eventually, Viserys pushes Daenerys too far - after he hits her again, she threatens to cut off his arm if he ever touches her again.
Viserys quickly becomes disenchanted with waiting for Khal Drogo to grant him an army. He goes into Daenerys' tent to steal the dragon eggs in order to sell them to set up his army but Jorah Mormont forces him to leave them alone, angering Viserys further.
Later that night, Viserys enters a feast for Drogo and Daenerys while drunk and demands his army. He unsheathes his sword - a grave offense in Vaes Dothrak - and threatens the life of Daenerys' unborn child, saying that unless he gets what he bargained for, he will take Daenerys back but Khal Drogo can keep the baby after Viserys cuts it out of her. In response, Drogo at last agrees to grant Viserys the golden crown he was promised. To Viserys' horror, Drogo melts down his belt and pours the molten gold over Viserys' head, killing him.
Viserys displays obvious Targaryen physical traits such as blonde hair and blue eyes.
He is obsessed with regaining his seat on the Iron Throne and will do anything to get it, going as far to tell Daenerys
"I would let his whole tribe fuck you, all 40,000 men and their horses too, if that's what it took."
As the series goes on Viserys becomes increasingly frustrated with the fact that Khal Drogo hasn't honoured their agreement yet, this sees him become progressively more violent.