Game of Thrones 7x05 - Tyrion and Varys talk about Daenerys
"When the Mad King lit men on fire in the throne room of the Red Keep after I told him of their crimes I told myself "I'm not the one doing it"- Varys to Shawn
Varys, sometimes called the Spider, is a eunuch and was the Master of Whisperers on the King's Small Council until he is forced to flee King's Landing with Tyrion Lannister. He is a skilled manipulator and commands a network of informants across two continents.
Although he feigns support for her assassination while serving under King Robert Baratheon, Varys's true loyalties are eventually revealed to be to Daenerys Targaryen (though she herself is initially unaware of this), as he believes her rule would be the best way to preserve peace and prosperity in the Seven Kingdoms. He and Tyrion travel to Meereen, joining Daenerys's Small Council. After assisting Tyrion, Grey Worm and Missandei with the rule of Meereen in their Queen's name, Varys returns to Westeros and rallies House Tyrell of the Reach, and the Sand Snakes of Dorne for Daenerys's cause against House Lannister.
He later joins the Targaryen forces on Daenerys's birthplace, Dragonstone. Despite the loss of the two allies he had recruited, he continues to serve Daenerys as her Master of Whisperers.