Down the Hatch is a secondary quest in the Side Effects premium module.
The sewers have been locked since monsters infested them recently. If I want to get in, I'll need to get the key from Sergeant Orel, commander of the mercenaries stationed at the sewer entrance. Like any good commander, he spends most of his time getting drunk at the Hairy Bear. I should talk to Sergeant Orel. Apparently, he spends most of his time at the tavern.
Sergeant Orel demanded proof that I'm a witcher. The only way to convince him is to beat him in a drinking contest. Looks like I have no choice — if I want to get in the sewers, I have to outdrink the mercenary. I need to drunk Orel under the table.
I managed to outdrink Sergeant Orel, though my liver probably hates me for it. Good thing I'm a witcher. In any case, I have the key to the sewers. I can now open the sewer entrance.