During the Indecent Proposal quest in Roche’s questline, you’ll encounter a mini-quest called The Ballista in The Witcher 2. As you enter Lorendo’s residence in Chapter 1, you and Roche must stay in the yard until Lorendo is free.
As you enter the yard, talk to Roche, who will tell you to see the guard guarding the Ballista and try to disable it, as it can be harmful later on. This starts the Ballista quest, and now all you need to do is disable the Ballista.
How to disable the Ballista in The Witcher 2
If you go up to the guard near Ballista, he will push you away, which won’t work. You also can’t fight as this would be risky. You need a distraction. For this, go to the right side of the yard, and you’ll find a woman by the wall. She is a prostitute named Margarita.
Talk to her and ask her to distract the guard with her charms in The Witcher 2. She’ll suspect you and even cost you more, so here are the right options.
First, choose the option “I wanted to surprise my friend,” as the other doesn’t do anything. Next, she’ll ask what you want her to do. Choose Your Specialty.
After this second choice, you can pay her according to your choice or do her a favor. The quest will move forward if you wish to pay in The Witcher 2. If not, select the Any other way I could convince you? Option and listen to her request.
She wants you to humiliate the two Lorendo men named Myron and Alphonse. End the conversation and go to the table. You’ll find both men sitting here. One by one, challenge them to an arm wrestling match. It’s easy to win against them. Just ensure the bar and button go opposite where you are seated, and they’ll lose eventually.
Once you’ve won both matches, talk to Margarita; she’ll take the guard away for a while. After the guard steps off the platform with Margarita, go to the Ballista and disable it in The Witcher 2 Assassins of Kings. This will end the Ballista quest. You can then continue talking to Roche and resume the Indecent Proposal quest.
There are no major consequences if you fail to disable the Ballista. Nothing happens afterward if the guard is away and you don’t do anything. However, if you disable it, you are shown in the cutscene that the Ballista doesn’t go off when you and Roche leave Loredo’s residence.