After reaching the bottom of Subterranean, the Slugcats must swim through a golden pool until they dive into the Abyss. In there only creatures that have been born from the void roam freely with a single objective, to help the rest in their final stage of ascension.
Void Worms are long, massive creatures that reside deep within the Void Sea in Subterranean Depths. They are the only creatures that are encountered in the subregion. Despite their sheer size and the absence of fins or any other appendages to aid in movement, they are able to move remarkably fast.
Void Worms have silvery bodies that stretch to an incomprehensible length. Their heads are disproportionately small compared to their bodies, with golden eyes and tentacle-like limbs with hooks on the ends. They can be encountered in the ascension endings for all Slugcats. Although Slugcat only encounters one Void Worm that actively interacts with them, there are many others that can be seen swimming in the background. Slugcat is forcefully moved in the same direction as a Void Worm when their body passes directly overhead, accompanied by a loud rumbling sound.
After Slugcat dives into the Void Sea and travels down a few screens, many Void Worms can be seen swimming around. Some Void Worms nearby can push Slugcat with the force of their movement. Swimming below the Void Worm swarm causes a Void Worm to appear with a unique rumbling sound. After looking at Slugcat for a few moments, they attach a thin strand to Slugcat, which they use to pull Slugcat upwards, then back to the depths of the Void Sea, traveling at a speed so quick it causes Slugcat to appear stretched and distorted. After a while, the Void Worm ceases movement and releases Slugcat before heading upwards again. Upon being released, Slugcat is left in a pitch-black abyss with only white light and music to follow to the ending of the game.
Guardians are large, mysterious creatures found only in Subterranean Depths and Rubicon. Their main purpose is preventing the player from finishing the game if Maximum Karma maximum Karma has not yet been attained.
Guardians are among the tallest creatures in the game, towering far above Slugcat. Despite this size, the only part of a Guardian that can be physically interacted with is their rectangular head; everything below is considered part of the background and can be walked through. Their heads are adorned with a red mark resembling the Maximum Karma tenth Karma symbol. This cross is dim when idle but lights up whenever the Guardian is provoked.
Right below the head are 4 thin arms gradating to a light grey, with two black rings around each. A series of beads hangs from each arm, seemingly connecting to their bodies, which get progressively darker the further they are down the chain. The arms can move independently of one another, but usually move in tandem. Additionally, these gestures seem to synchronize with the halo, which is made up of rings filled with various glyphs seen nowhere else in the game orbiting around the center in alternating directions. Magnifying rings skim across the halo, linking together various glyphs and shifting them around. This projection may change size, even gaining additional rings depending on what the Guardian is doing. It typically stays the same size while idle but grows when aggravated. Occasionally, when their heads move, projecting lines between it and their halos may be seen briefly.
Guardians are stationary and passive by default, ignoring all and any creatures until provoked. They enter a somewhat aggressive state if any creature attempts to walk by them without having attained the highest karma level, with aggression increasing on each repeated attempt. In this state, their halos grow larger and the marks on their faces glow a bright red.
When angered, Guardians use their telekinesis on whichever creature aggravated them. Any creatures or objects near the target are also affected, which means that, even with maximum Karma, Slugcat may still be moved around if they bring a creature that triggers the Guardian's aggression with them. Guardians first launch Slugcat away in the direction from which they came. After sending them back a second time and being approached a third, the Guardians begin violently slamming Slugcat into the ground until they die from fall damage. With other creatures, the Guardians skip the first step and proceed straight to attempting to kill the creature, though this does not work due to the fact that no creature other than Slugcat is affected by fall damage.