The Cave

The Cave on Your Factorio Server

The Cave by behroozzx turns Factorio into an underground adventure: dig, explore, and loot hidden treasures, special caverns, and depth-based difficulty from Easy to Nightmare. It layers in reworked digging, balanced ore and oil progression across eight resource tiers, optional challenge modes, train interiors, research upgrades, and a coin market. Brave the optional Dark Zones and you'll have just 30 seconds to place lights before the darkness turns deadly.

For your multiplayer group, that's a substantial new experience on the same server. Installation is standard: drop the zip into the mods/ folder and enable it via mod-list.json. Since your server automatically syncs mods on connect, every player experiences the cave expansion from their first login.

Tip: Agree on a difficulty tier as a group before tackling the Dark Zones together.

Plan the rollout and operation

Treat The Cave like a scenario or major overhaul. Start a dedicated world, agree on difficulty and challenge modes, and allow extra time for generation and exploration. Test digging, Dark Zones, train interiors, the market, and saving with at least two players. Add other overhauls only afterward; competing ore progression or world generators can otherwise create problems whose cause is difficult to isolate.

For rollout, copy the save, mod-list.json, mod-settings.dat, and current mods directory. Enable the new zip on a server copy first and let Factorio validate dependencies and version ranges during boot. Connect at least two clients, use the core feature, save under a new name, and load that save again. Watch the server log, UPS, and synchronization in a realistic factory rather than only on an empty map. For updates, record the game, mod, and dependency versions together and change one package per test run. Content or recipe mods can leave saved entities and production chains behind, so do not remove them directly from the live world. On a copy, replace recipes, filters, and buildings before deleting the file. The original save then remains a reliable rollback. Also document the tested mod order so teammates and later maintenance windows always begin from the same reproducible combination.