Quick Answer
Modern axe improves survival and building, rebreather unlocks underwater routes, and keycard opens the major story gate. Treat them as a progression chain: upgrade safety first, unlock traversal second, then push story access.
Item route
| Item | Get it when | Do not go if |
|---|---|---|
| Modern axe | You can handle a moderate cave trip and want safer combat/building | You have no light, armor, or meds |
| Rebreather | You are ready for water routes and later cave progression | You cannot survive cave enemies or find exits reliably |
| Keycard | You are preparing story progression and ending access | You have not prepared rebreather, food, meds, and return plan |
Supplies before the route
- Full food and water before entering.
- Extra cloth, light, armor, and meds.
- A marked surface route back to base.
- Enough inventory space for key items and cave loot.
- A save before major cave pushes.
Common mistakes
- Rushing the keycard because a guide says it is important.
- Treating the rebreather as optional when planning ending routes.
- Going for modern axe with no armor and losing supplies repeatedly.
- Forgetting that the best route is the one you can exit safely.