The story tells, that the character lands on a alien planet. Why is there a human-friendly atmosphere with oxygen?
Providing the player with new tools or adjusting the game interface, without fundamentally changing gameplay.
Stuck on an ice world with seas of methane and and an ammonia atmosphere. The only organic material on the planet appears to be a vicious native animal! Can you survive long enough to escape?
Collections of mods with tweaks to make them work together.