Invasion of Cintra
Cahir leads the Nilfgaardian army in battle against Queen Calanthe, King Eist, and the Cintran army in a field just outside Cintra. However, the Cintran army is decimated by the invaders as, unknown to Cintra, Nilfgaard's mages had wiped out all possible Skelligan reinforcements at sea by causing a massive storm. Cahir personally fires the arrow that pierces Eist's eye, instantly killing the king and forcing Queen Calanthe and her remaining soldiers to retreat.
Nilfgaardian forces then make their way to the city and begin to slaughter everyone within the city's walls while Cahir goes looking for the princess, soon spotting her as she's escorted out of the castle on horseback. As Ciri and Sir Lazlo attempt to flee from Cahir, Lazlo is killed by one of Cahir's arrows, and the dead knight's body ends up dragging Ciri off the horse as the body falls to the ground.
Having caught up with Ciri, Cahir takes her prisoner and races off on horseback, hastily leaving the burning city behind. However, on seeing this sight, Ciri screams, releasing a powerful magical pulse that scares Cahir's horse, knocking them both to the ground. As Cahir tries to grab her again, Ciri releases several more screams, each time getting more and more powerful, preventing Cahir from getting her as she puts more distance between them. After one such scream, a nearby stone monolith collapses and causes the ground to split and create a chasm between the two, allowing Ciri to escape.
Searching for Princess Ciri
Cahir and his men invade a Cintran refugee camp in the late hours of the night, slaughtering everyone in their path, in search of Ciri, who manages to escape unseen.
After conquering Cintra, Cahir and Fringilla search for Queen Calanthe's body. They find her on the ground, buried underneath the snow. One of Fringilla's comrades slices a piece out of Calanthe's arm and eats her flesh. Fringilla then guts him and is able to determine that Ciri is in Brokilon forest. One of his men suggests sending soldiers in to take Ciri, however, Cahir knows that armies are not the way into Brokilon forest.
Retrieving Ciri from Brokilon Forest
Cahir seeks out the help of a doppler in order to retrieve Princess Ciri from Brokilon forest. Cahir takes him to Mousesack, who they've captured. Cahir orders the doppler to take on his appearance. Cahir releases Mousesack from his chains only for the doppler to tackle him to the ground and shape shift into him, before stabbing Mousesack with a knife. After killing him, Cahir demands that Ciri is brought to him alive.
Cahir captured Ciri in the woods as she fled from the Adonis. If it had been any other way to extract Ciri, he would've done it. All he'd ever wanted was to fulfill her destiny. The White Flame had brought them together. She was the key to everything. As Cahir was fetching something to eat, he was confronted by the Adonis, who had taken on his appearance and in doing so, discovered what Ciri truly was. A fight ensued and Cahir was stabbed in the process, allowing the Adonis to escape.
Cahir murdered everyone inside the tavern to insure they weren't the doppler. As Fringilla cleaned his wound, she remarked that a simple test of silver would've sufficed. Fringilla stated that they could pull more soldiers and keep searching for Ciri. Fringilla reminded Cahir that it was he who rose up against the Usurper and helped free their people from their chains. She witnessed the White Flame crawl on him and anoint him. Ciri may be the key, but Cahir was the commissioner. They will find Ciri and spread the White Flame's supremacy throughout all kingdoms.
Battle of Sodden Hill
After discovering that the Brotherhood was fortifying the keep, Fringilla reported back to Cahir to alert him of their arrival. The field Marshall recommended that they fall back, but Fringilla desired to move forward with the plan. This was their chance to honor the White Flame. Cahir refused to lose Princess Cirilla and ordered Fringilla to tests the Brotherhood's defenses.
Fringilla and Cahir watched from the top of the hill as their men were taken out by the brotherhood. They were forced to move to the other front. Vilgefortz portalled to Cahir's destination, taking out half a dozen soldiers before getting to Cahir. During the fight, Vilgefortz was disarmed multiple times, each time using magic to return his sword, despite Yennefer's warnings to reserve his chaos. Vilgefortz is bested by Cahir and with his chaos depleted, Cahir kicked him off the hill. Cahir rolled down the hill and hit his head on a tree stump.