Chimney
Return to the Chimney and climb up a floor to find a rocket platform. Stand on top of it and examine it, and you will fly up to the top of the Chimney's map. Make your way up, keeping cautious of the wind blowing from either side.
Devil's Garden
The Devil's Garden is broken up into four puzzles, each with their own predetermined method to find a path forward. Head to the door on the left to begin the challenge. There's no turning back!
In the first section, the correct door
The solution:
In the second section, the correct door
The solution:
In the third section, you will be presented with a symmetrical cross-shaped
room. The correct door
The solution:
In the final section, moving forward will place you back where you started. When you find your way out, continue to...
Once-Sacred Ground
There are several things to watch out for here, but they can be largely mitigated by taking your time. Butes, the small angel-like enemies, will drop in from the ceiling or floor based on how deep into the area you've travelled.
Another enemy that will reinforce 'taking your time' are Deleets, which will count down for five seconds before exploding and opening the path forward. After the final two of these, you'll be faced with a familiar boss.
BOSS: Heavy Press
Heavy Press will stay up against the ceiling, slowly becoming uncovered as you deal damage. It will charge and fire a bolt of lightning directly under itself every so often.
Rolling enemies will travel around the outside of the arena, and Butes will fly in from the floor on either side in a slow, but continuous pattern.
The strategy for this fight:
After defeating Heavy Press, get out of the way and let it break a hole in the floor. Fall down after it into an intermediate path leading to The Observatory.