Much like Armored Warrior, Long-arm Centipede Sen’un is a mini boss found in the Senpou Temple region in Sekiro: Shadows Die Twice.
Head to the Sculptor’s Idol at Temple Grounds. Drop down on to the roof below you and then jump and grapple to the branches that reach out over a small lake. Jump up and walk down the side of the building and take out the Monk stood by tree in the corner.
Jump on to the small ledge and then double jump on to the next ledge. Turn right and run all the way along the front of the building and follow it around to the left at the end. Drop on to the roof of the building on your right, run along it and then drop down to the entrance.
There are two Centipede’s in the entrance. Take out the first one with a stealth Deathblow and then kill the other. Long-arm Centipede Sen’un is on the other side of this wall, but we have some preparation to do before we take him on.
Grapple up to the beams that hang over the room. There are two Centipede’s up here that we need to take out first, so grapple over to each one and take them out.
It’s likely that you’ve now aggro’d both the boss and the other two Centipede’s who lurk down below, so head back to the safety of the entrance door and run a little bit up the hill. Wait it out here until the music stops, signifying that we’ve lost the aggro.
Now, head back through the entrance and grapple up to the beams. The boss and his Centipede mobs won’t be paying attention to you. The next step is to take out the two mobs so that we can fight the boss in peace. To do this safely we’re going to have to take each mob out one at a time, so drop down and Deathblow one, grapple out and run back to the entrance to lose the aggro, then repeat the same step for the second one. After you kill the second one, make sure to grapple back out and head to the entrance to lose the aggro. Do not try to take the boss on directly after taking out the second mob, you’re only making life hard for yourself.
If you’ve followed these steps correctly, you should now be stood at the entrance door, with all of the mobs dead and no aggro. Grapple up to the beams again and the boss will be stood below, somehow completely oblivious to your presence. Long-arm Centipede Sen’un takes two Deathblow marks to kill, so drop down and Deathblow him from above to take one down instantly.
The next part is usually the hardest, but Long-arm Centipede Sen’un is actually really easy to beat. He attacks really quickly—so quickly that you can be dead in seconds—and he barely stops for a breather. Because of that, our tactic is quite simple. Forget your attack button, there is absolutely no point. All we’re going to do is Deflect, Deflect, Deflect. Such is the speed and regularity of his attacks that his Posture bar will fill rapidly, so you can actually finish this fight in lightning quick time if your timing is good enough.
On occasion he will throw a slight curve ball your way with a Perilous/Red Kanji attack, where he swipes at you with both claws in a pincer-like movement. If he does this, jump up and jump again when you’re above his head to jump on him and cause some more Posture damage.
Keep at this tactic of Deflecting continuously and performing a Jump Kick when he goes for a Perilous attack and you’ll open Long-arm Centipede Sen’un up for that killer Deathblow in no time. Remember, forget about attacking, it isn’t necessary.
Killing Long-arm Centipede Sen’un will earn you a Prayer Bead and some Yellow Gunpowder, which can be used for explosive Prosthetic Tool upgrades of intermediate and higher rank.