The Flame Vent is one of the prosthetic attachments you can find early on in Sekiro: Shadows Die Twice. In case you’ve not managed to find it yet here’s a handy guide. You will find the Flame Barrel (needed to make the Flame Vent back at the Sculptor) not far after the Hirata Estate Idol. There are loads of enemies patrolling the area so take your time as you battle through so you don’t get outnumbered.
The most annoying guy has to be an archer on the roof just above the Flame Barrel itself so take him out as soon as you can. There are also dogs roaming about plus a few enemies you might miss at first glance as they are slumped against walls.
The Flame Barrel is actually in the bonfire beneath the archer I mentioned before. For full details have a look at our video below:
The Flame Vent is especially effective against monsters with red eyes. If you haven’t already fought the Chained Ogre yet I recommend you get the Flame Vent before you do as it makes the fight much easier.