This is the second companion quest with Petrus. There is a requirement that you win at least the 3rd challenge in the arena before you can do it.
The quest is started by talking to Petrus at some point after the Vices of the Mother Cardinal quest is completed. The first thing to do is to travel to San Matheus and talk to the book maker in the basement of the tavern, he’ll agree to set up a fight with an old champion so the next thing is to talk to Candy Cane but if it’s not night you’ll have to take a nap. Candy Cane can be found in the same location as the last quest down near the port.
You’ll have 2 options, charisma let Petrus speak or ask Candy Cane to fix the fight which will cost you 250 coin, if you try to negotiate you’ll end up fighting Candy Cane and his men, if you refuse to pay you’ll also end up fighting, however in both cases after you defeat Candy Cane and search his body you’ll find a key and a letter from the Mother Cardinal asking about the fight between the legete and a veteran of the arena and if she should take an interest. She expects to hear from Candy Cane shortly using the usual dead drop. The key is for the dead drop. Petrus will write a fake letter to put into it. To find the dead drop from Candy Cane’s location retrace your steps until you get back to the tavern, go past the tavern and around to the left then straight until you can go left, you’ll end up fighting only 3 bandits and the dead drop is in the middle of that street. If you go the other way around you’ll end up fight a bigger group of bandits. Once the letter is in the dead drop you’ll have to wait 24 hours.
I used my charisma and petrus was able to convince Candy Cane to fix the fight but it was with a warning to not try and win, so I don’t know if that’s going to come back at some point. Now you’ll have to wait for 24 hours for the fight to take place in the arena. You’ll have to fight alone and as soon as you say I’m ready the fight will begin. The veteran had the same amount of armor as I did but he wasn’t to hard to beat, it’s even easier if you use your gun . It doesn’t look like you make any money , so after the fight go and talk to the Mother Cardinal. A long cut scene will play but all does not go Petrus’s way though as Cornellia reveals a secret involving De Sardet. You’ll earn 1300 xp.
Thanks for watching and happy gaming