What's the best way up from layer 4?

[DRayX]

Once you beat the layer 3 interference unit, you can fast travel to layer 4, but you can fast travel back up from layer 3. My route up through 3 seems sort of brute force, and I feel like there has to be a better way.

From freezing hot mines, it seems like the only way you can go is Rock Slide Hall (the Quadruple Pit exits from Glass Layer are inaccessible, and the ice wall prevents using Cold Heat Layer).

[AFRO THUNDER]

Someone mentioned that in the chamber where the splitjaw is, if you climb up a wall far enough you get to blow a whistle and kill it in one stroke, and it also makes a path up to the exit. Haven't tried it myself though.

[DRayX]

Yep, that's totally it, all of the upwards paths along that route make total sense. Thank you so much.

So, the best route up through layer 3 I can come up with is: Freezing Hot Mines -> Glass Layer -> Quadruple Pit -> Hexagon Pillars -> [Cold Heat Layer -> Updraft Wasteland] or [The Great Fault -> Heaven's Waterfall] depending on your preference (Updraft Wasteland is quicker for fast-travel, Heaven's Waterfall for a full ascension with no fast-travel). That's way better than my super iffy brute force up Rock Slide Hall.

For anybody else looking routes up:
Layer 1: Multilayer Hill -> Wind-Riding Windmill -> Tree/Fossil Abode -> Waterfall Gondola -> Netherworld Gate -> Orth
Layer 2: Heaven's Waterfall -> Seeker Camp -> Hell's Crossing -> Inverted Arbor -> Corpse-Weeper Den -> Forest of Temptation -> Multilayer Hill