Beat it
Before you say anything: yes there’s spoilers below for the Giant Snek, also known as the “Great Serpent.”
He’s been in trailers for over a year. I even used a generic header image for him despite the custom images below.
Location/mechanic/encounter spoilers!
Step one: Run from the snake and wound it
Once you hit the “Underbridge Valley” idol waypoint, you’re going to get attacked.
Most of the encounter will involve running and hiding, so look for the rough-edged walls to shimmy on and hang from. Spamming dodge when you’re out in the open and immediately consuming a gourd for health is also a completely viable tactic: all you need to do is survive roughly a minute while moving forward.
Once you see a tent, this is your opportunity to actually end the encounter. Hide in it, then wait for the red dot to appear on the snake’s eye after investigating it. Slash ’em and you’re good!
The second instance of the snake in the lake (good movie title) after the Gun Fort is way easier. If you haven’t figured it out yet you can spam the circle (B) button to swim incredibly fast. Just head to the right side of the map facing the way you came in, go around/under the log, and land. There’s a checkpoint there and you can freely explore the area afterward without fear of snake bites.
Step two: Feed the cave snake (conspiracy unmasked: there are two snakes) and avoid it
To do this you need the Puppeteer Ninjutsu after acquiring the Mortal Blade in the campaign (you’ll get it automatically as part of the story, roughly halfway) or some luck (which I’m dubbing the “Chris Carter Brute Force Strat”). I’ll explain both methods.
From the Bodhisattva Valley waypoint idol, look down at the ravine on the opposite side of the boss bowl: you can actually go down there into an optional area that turns into a shortcut. Fall down and grapple on trees until you hit the floor. Head right at the fork in the road and into the cave of the serpent.
You can explore here or simply solve the puzzle and explore later. Once you get to the room with the snake guarding the small pass, head left and use the puppeteer ability on the cowering monkey. They’ll act like an idiot and distract the snake, allowing you to grapple up and run into the room (this is an alternate route into the Ashina Depths and all optional).
Or, you can brute force it. Walk as far as possible on the pass to bait the snake into an attack: dodge, then sprint forward (hold circle/B) and subsequently get hit on purpose. When you die, immediately spam the revive button (R1/RB) and sprint forward again. You can make it into the room with practice without having to commandeer the monkey. If you have issues, try to spam roll after reviving. Grab the item from the shrine then grapple up for a waypoint idol.
Amazingly, this is a second snake! It will still appear even if you kill the one below.
Step three: Kill the snake.
For this one you will need the puppeteer ability.
Head to the Senpou Temple idol waypoint. Go out of the door and hang right. Look down at a little inlet, and sneak up on/go backstab the enemy and use puppeteer: they’ll fly the kite for you. Turn around and go up the mountain pass and into the temple. Head out of the window and look up at the huge tree in front of you. Scale it, then at the end you’ll be able to grapple across the gap thanks to the kite, which is now airborne.
At the end of the path is a plank that you can use to kill the snake. That’s it! Just don’t forget to lock on before you leap and use the finisher twice when it prompts you. Trophy/achievement unlocked!
