I am a chaos gremlin, but more importantly I think terror is what makes subnautica so special and invigorating (There are some great youtube videos on this topic). The constant apprehension and fear of dying. So here are my two ideas to keep even veteran players on their toes and keep the fear alive.
Then, as it sinks back into the hole, it creates a vacuum that sucks in other players if they get too close. Try to scan it as it sinks back in? Sucked into the hole and eaten. Essentially a leviathan sized bobbit worm that could eat the collector leviathan if it got too close, and serves no purpose but to terrorize players. Would probably stick it on the edge of the void, or somewhere there’s already not much reason to explore. Or alternatively somewhere important to keep players on edge when they have to come back.
Frequent Visit Geography Triggers
As players progress in the game, areas they visited earlier become mundane as the fear subsides. They know what’s there, they know it’s safe. I propose small environmental change events after a certain number of visits. For example, as a player passes through an invisible trigger zone for the 3rd time, a mudslide occurs. As they approach a rock pillar, it collapses. They would be cutscenes, like the aurora exploding. Can’t be moved afterward, just keeps the map fresh after exploring for a while. Don’t need a ton, just a handful scattered around to keep things fresh.
Frequent Visit Attack Triggers
Same concept as the geography triggers where a certain amount of visits triggers an event. But this would include hostile entities. For example, a player who passes through the area multiple times would trigger a hostile entity to emerge from a nearby cave to attack. After the player leaves it would despawn and either not happen again, or reset and occur again randomly. This way the player is always on edge, not knowing where the next attack will occur.
These triggers would allow the map to stay fresh months or even years after the game is released. I know I still play the original subnautica, and having environmental changes or risks that I don’t expect would make it so much more invigorating to play a game i’ve finished.