Chained Ogre is an optional mini-boss in Sekiro: Shadows Die Twice.
Located in the interior of the Ashina Castle after defeating both the Headless Ape and the Corrupted Monk, he’s very similar to the Chained Ogre that you had to fight early on in the game in the Ashina Outskirts. Thankfully, we can cut this fight in half straight away with a stealth Deathblow.
From the Upper Tower – Antechamber Sculptor’s Idol, run up the stairs and kill the first enemy. Then run into the central room and you should be able to stealth Deathblow the other enemy in here too. Now, jump over the railings and grapple onto the beam in the middle. You’ll see the Chained Ogre below, so either shimmy along the beam until you’re above him or jump off the beam and position yourself above him and you’ll be able to hit the first Deathblow and cut the fight in half straight away.
From here on out it’s all about avoiding his attacks and waiting for your own opportunities. You’re fighting in a pretty confined space which makes it more difficult, but try to use the central island to your advantage, circling around it to give yourself a degree of separation between yourself and the boss. He has a number of attacks but they’re all pretty easy to avoid; you can Deflect his normal attacks if you want but they do a lot of Posture damage, so instead I recommend just dodging all of his attacks by jumping backwards and sideways, unless you know you can’t get away, in which case Deflecting is your only option.
His attacks include dropkicks and elbow drops, and it’ll take him a couple of seconds to recover from both of these, so jump out of the way and then jump back in to get a couple of your own hits in. The same can be said for his Perilous/Red kanji attacks, one of which is a standing grab which you can jump backwards out of the way of, and the other is a diving grab where Chained Ogre covers a fair distance, so I’d recommend jumping sideways out of the way of it if possible.
Keep it up and eventually you’ll do enough damage to him that you’ll be able to break his Posture and get in a killer Deathblow.
Killing him will earn you a Prayer Bead and Shinobi Medicine Rank 3, which is a latent skill that increases the healing effect of recovery items.