About:
Wiggler is a Deepest Sword secret achievment.

Description:
Bypass the last section with the length 4 sword.

How to get:
When you get the Lengh 4 Sword, make it to the 4th level of the cavern, then go as forward as you can (without climbing on anything) and there is gonna be a wall. Stay as close as you can to the wall and then press M2 (right click). Your sword is going to attach on the top of the wall then try to wiggle around untill you reach it.

I Hope that i've helped you! :)