Lifting the Princess' Curse
For the last six years, citizens had been disappearing throughout the land of Temeria. So, Triss Merigold sought out the help of renowned witcher, Geralt of Rivia, to stop the creature that has been terrorizing the city and kingdom. Triss presented Geralt to King Foltest, Lord Ostrit, and Captain Segelin, with whom she pleaded with to enlist Geralt's aid. They claimed that the creature was actually the daughter of Princess Adda, who was murdered. However, Segelin was sceptical of Geralt's claims. Triss hoped that the king would allow her to search the abandoned castle for clues as to who killed Adda, however, Segelin feared that Geralt would kill the princess. Geralt explained that the creature grew inside of Adda, feeding on her womb and mutating, growing for years until she got so hungry that she was forced to "slither out". Essentially an "overgrown abortion". This angers Foltest, and he commands that everyone leave.
As they left the room, Geralt pushed Segelin out last and locked the door behind them. He took that time to ask the king who fathered Adda's child. He also questioned why Foltest never married and produced his own heir. Not to mention the fact that he had allowed for the striga to live. All this pointed to King Foltest being the father of the striga. Foltest surmised that the rumours of witchers being devoid of heart and emotion must've been true in order for Geralt to accuse him of an incestuous affair with his sister while simultaneously advocating that he kill his own daughter. The guards broke through the door, and Foltest ordered Geralt to leave Temeria and never return.
With Triss' advice, Foltest had a change of heart and decided to trust Geralt and take his help after all. He met Geralt at the entrance to the abandoned crypt, where the striga slept. Geralt honestly answered that he didn't know if this would work or if the princess would be normal if she was cured. All she'd ever known her entire life was "rage and hunger". Geralt gave Foltest a gift to give his daughter in case the curse was lifted, but Geralt didn't survive through the night. Foltest claimed that both he and Adda initially tried to resist their urges, but what they felt was too powerful and "for all it brightens, love casts long shadows". He envied Geralt's mutation to live and never have to fall in love.
After Geralt managed to successfully lift the curse, King Foltest issued a statement that Lord Ostrit gave his life defeating the creature. He returned Geralt's gift to the princess along with his coin.
Battle of Sodden Hill
King Foltest agreed to defend the keep on Sodden Hill and rally the Northern Kingdoms after getting word of Nilfgaard's plan to conquer the continent. He arrived with the Northern armies shortly after Yennefer set the entire hillside ablaze.