At some point, he and his friend Valdo joined the travelling circus.
In 1272, Valdo made friends with Ciri while they were traveling Novigrad and helped her to escape the Wild Hunt, who were pursuing her. Valdo and his troupe introduced Ciri to Bea, who helped her find Dandelion.
Geralt and Ciri met him in the Farcorners of Novigrad, where they thanked him and Valdo for looking after Ciri. Aegar left as he needed to find a new horse, as their horses had either died or were two weak to haul anything.
Once he returned, he explained the deal with the merchant had not worked out, so he was going to sneak into the man's stable and steal some horses.
If Geralt agrees to steal the horses: after agreeing to the plan, they went to the docks and Aegar kept watch while Geralt snuck in and opened the door for them. After calming them, the three of them stole four horses and galloped through and then out of the city, back to the circus camp. Ciri and Aegar were overjoyed and thanked Geralt for his help, before the the witchers said their goodbyes and left.
If Geralt refuses to steal: Ciri urged Geralt to consent to Aegar's plan, though he wouldn't budge. Aegar argued that it was up to Ciri whether she came, not the witcher. Eventually things got heated, and Geralt ended up getting into a fistfight with Aegar, which caused Valdo to ask them to leave, much to Ciri's disappointment.
If Geralt offers or asks Aegar to pay for them: trying to avoid thieving, Geralt offered to pay for the horses personally or have the elf pay, though Aegar explained that the merchant didn't have a problem with the amount of coin, but the fact that he was a nonhuman.