What the achievement asks
Clear Layer 8 of Twisting Corridors. Ten points, account-wide, and the Corridor Creeper.
Twisting Corridors is Torghast at eighteen floors instead of five, and the eight layers open in order. Layer 8 therefore means running all eight, which is a hundred and forty-four floors.
It is no longer hard, it is long
In Shadowlands this was brutal, and the comments from 2021 are people describing hours lost on the final floor. None of that applies now. A current character walks through it.
What has not changed is the walking. Eighteen floors of corridor per layer, and even skipping every fight you can, the travel is the run.
Treat this as a movement problem, not a combat one. Everything below is about going faster, because nothing else is going to stop you.
Go faster
Buy a mount inside. Farm 250 or so phantasma on the first two floors and buy a Ravenous Anima Cell from the broker. It rolls mobility powers such as the Mawrat Harness, the Maw Seeker Harness and the Glasswing Charm. Getting mounted early changes the whole layer.
Take movement powers over damage. The super-jump power, anything that adds speed, anything that makes mawrats explode. You do not need damage.
Stack speed from outside. Maw-Touched Miasma from Ve'nari, 230 Stygia, plus a speed food such as Fried Bonefish.
Two practical notes
Groups get the same credit as solo runs, and everyone in the party earns the layers. If you have someone to bring, bring them.
The wing you start in is rolled, and people avoid opening a Twisting Corridors run in Coldheart Interstitia. If you have the option, take a different one.
The reward
Layer 8 hands over the Corridor Creeper, which is the actual reason most people finish this rather than stopping at layer 5.