Cave

The Cave or "Cavern" is the second chapter in struggling, here, the cave serves as a dumping grounds for the Laboratory's failures. It has plenty of confused and difficult to traverse terrain, and the hazard's happen to be acid, lombrics, gears, and lombric spikes. Rats are also a hazard in the cave, should you go to the secret area, his highness's nest, in the mechanical bone-crushers section. This chapter is the first chapter to introduce a boss, in which it is Amadeus the Firstborn. The chapter itself goes with a dark cavern setting.

This chapter music is as follows: Hangover lullaby, flesh opera: cries of the firstborn, deep depths, his highness nest(secret area) chasing rats(secret area) and a song of acid and bones.

this chapter has 5 exclusive achievements and 10 obtainable hats. It is preceded by the Laboratory and succeeded by the canyon.

Cave I - Mine of Mistakes
This is the first area of the chapter, and the first time troy is out of the lab. It only consists of difficult terrain and acid.

Cave II - On the step of the Firstborn
Also another short area, in which it's just spewing acid pipes, in which some can be plugged, but it is not over yet, after that, you finally reach Amadeus. Here, you are greeted with the task of curing the firstborn's cancer by physically damaging the tumors that are infecting her, after this is done, Amadeus will set you free and bless you with the first Abomination God Blessing, Remote Arms, which is the ability to detach troy's arms from him, and therefore, there will be future challenges involving the ability.

Cave III - Trials of The Glittering Mine
As mentioned above, this area contains several challenges involving Troy's new ability to detach his arms.

Cave IV - Lombric Hunting Ground
This is where lombrics(who are giant, red, stationary worms with sharp teeth and covered in crystals)come in to play, and this area is full of them, troy must use his arms as a means to bait them so he can carry on.

Cave V - Mechanical Bone-Crushers
Gears will be present in this part of the chapter, in which troy must use them carefully, and if not careful, will get crushed by them. This is arguably the hardest part of the cave chapter. Do note: Gears can be destroyed by rocks.

Cave VI - Lab Intern's Prototyping Area
Yet another section that advocates the use of remote arms. Once the puzzle is complete, troy can carry on as usual, such as avoiding lombric spikes and acid pipes.

Cave VII - A Song of Acid and Bones
This is the final area in the cave, in which amadeus makes an appearance, but amadeus isn't the only one making an appearance, the rat king does so as well, in which he orders a rat to release the acid, in which the rat succeeds but ends up killing the rat king and himself, and presumably Troy to if he doesn't play it fast and safe, it also consists of lombrics. At the end, explosives are triggered and a goat, a scientist, a lombric and amadeus all freak out. The explosion happens, leading troy to the middle of nowhere.

Aftermath
After the explosion happens, troy will be sent to the middle of nowhere, also known as the canyon, where he has no choice but to continue through this unknown environment.

Trivia

 * This is the first chapter to introduce an abomination god, in which it is Amadeus the Firstborn.
 * This is the first and only chapter where giant arms are present, in which they are attached to the environment while leaving troy armless.
 * This is also the only chapter in which the rat king appears.
 * This is also one of the two chapters where you get an abomination god blessing, in which it is remote arms. The other being canyon, with time alteration.