Guide to the Otherworld in Fortress Saga

Beyond the Walls: A Beginner’s Guide to the Otherworld in Fortress Saga

Your fortress is rolling, your heroes are summoned, and the main story is progressing nicely. Then, a new icon appears: Otherworld. It is easy to ignore this mode while you focus on the campaign, but doing so is a mistake. The Otherworld is not just a side activity—it is a primary source of the materials you need to upgrade your Treasure Research Institute (宝具研究所), one of the most significant long-term power boosts in the game.

This guide will explain how the Otherworld works, how to explore it efficiently, and how to score high in its competitive Occupation Battles, all without drowning in the details.

See also : Beginner’s Guide to Fortress Saga: AFK RPG

See other game guides : Guides and Walkthroughs in Gaming

What is the Otherworld?

The Otherworld is an exploration and territory-control mode. You send your fortress into different regions, clear stages to increase an Exploration Rate, and then use that territory to compete against other players in Occupation Battles (占領戦).

The core loop is simple: Explore a region until it hits 100%, then challenge the current occupier to take it for yourself. But the rewards and the strategy run deeper than that.

How to get to Otherworld

Step 1: Finish the tutorial
You need to have your fortress named and have cleared the first few Adventure chapters. Otherworld is locked until you understand the basic loop.

Step 2: Clear Adventure Story Mode to the unlock stage
In the current version (2.x), Otherworld unlocks after you clear the early Adventure — around Adventure Chapter 4 / Stage 40-50 area. The game will show a pop-up: “Otherworld Content Added.”

If you don’t see it, you haven’t pushed Adventure far enough yet.

Step 3: Tap the Otherworld button
On the main lobby screen, look at the bottom/right menu:

Main Screen > World Map / Portal Icon > Otherworld

It’s the purple portal icon, separate from Adventure, Dungeon, Arena, and Sanctum. Tap it and you’ll see the list of available Otherworld regions.

Step 4: Enter a region
Pick the first region (usually the Normal Otherworld / first collab world). Tap Enter / Explore, choose your Exploration team, and start dispatching.

You don’t need to beat it in one go — Exploration % builds up over time with dispatches, just like idle farming.

The Golden Rule: Get Every Region to 100% at Least Once

When you first unlock the Otherworld, your immediate priority is to bring at least one region to 100% Exploration Rate. Why? Because the Treasure Research Institute requires specific enhancement materials that only drop from designated regions.

If you neglect a region, you will eventually hit a wall where you cannot upgrade your treasures because you are missing that region’s unique material. Spread your exploration across all available regions until each one has at least one 100% zone. Once you have that baseline, you can start pushing regions that have materials you are currently short on.

Efficient Exploration: Finding the Sweet Spot

The Otherworld is an idle-friendly mode. You can park your fortress in a stage and let it auto-clear enemies for loot. But the stage you choose matters.

You want to find a stage where your fortress can push enemies to the far right edge of the screen consistently. If you go too high, your fortress will get stuck or sink frequently, slowing your clear speed and reducing your rewards. If you go too low, your gold and experience gains per minute will be poor.

Start at a comfortable stage and gradually increase it until you notice your clear speed dropping. Once you can comfortably idle at a higher stage, move up. The higher the stage, the more Occupation Battle points you earn when you eventually fight for territory.

Watch for Flying Enemies

Starting from Stage 11 of the Otherworld, small flying enemies begin to appear. Your fortress’s default cannons may not be able to hit them. You must include at least one ranged-attack hero in your formation to deal with airborne threats, or your clear speed will plummet.

Occupation Battles: How to Win and Score High

Occupation Battles are the competitive heart of the Otherworld. Once a region hits 100%, you can challenge the current occupier. Winning grants you the territory, which provides passive benefits and ranking points.

Push Exploration Beyond 100%

Here is the most important trick for high scores: do not stop at 100%. If a region is already at 100% and you are preparing to challenge its occupier, keep exploring it further. Pushing the Exploration Rate above 100% increases the Occupation Battle points you earn from defeating monsters in that region. This directly boosts your final score in the battle, which may give you rewards.

What actually happens after 100%

Once a Otherworld region hits 100% Exploration, you keep getting Explore Rewards, There is no official ratio published by CookApps for it, and the game doesn’t show you a % -> material conversion table in-game. What players have figured out from testing is this (may change over updates) :

• 0% – 100%: 100% rate — you get the full first-time exploration rewards (Gold, Hero EXP, Fortress Parts material, Otherworld Coins, etc.)
• 100% – 150%: roughly ∼10-15% of the normal rate per exploration tick
• 150%+: drops to basically ∼5%

So if 1 exploration at 50% gave you, say, 100x Material, the same exploration at 120% will give you ∼10-15x Material, and at 180% it will be ∼5x.

Check the Stage and Season Rules

Before you challenge an occupier, verify two things:

1. The stage level. If you challenge at a stage that is too low, your Occupation Battle points will be too low to win, even if you clear the enemies. Make sure you are at the highest stage you can handle.
2. The Season Rules. Each Occupation Battle season has specific buffs and debuffs. Check them before you commit. A formation that works normally might struggle under a season debuff, and you may need to adjust your heroes.

Avoid “Stopping” Heroes

Occupation Battles are a race against the clock. Heroes whose skills cause them to stop moving or pause (like Zelos, depending on the build) will slow down your clear speed and cost you points. Prioritize heroes with fast, wide-area attacks and minimal animation lock.

Don’t Waste Your Occupation Battle Tickets

You receive one Occupation Battle Ticket per day, and you can hold a maximum of five. If your tickets are full and you do not use them, you are wasting free opportunities for territory and rewards.

If you want to push harder, the shop sells an Otherworld Occupation Pack (異界占領パック) in the Weekly section, which provides additional tickets.

A Final Word

The Otherworld is not a distraction from the main game—it is an integral part of your long-term growth. The Treasure Research Institute upgrades you unlock with Otherworld materials will boost your fortress and heroes in every other mode, including the main campaign and the Arena.

Get every region to 100% at least once. Find your idle sweet spot. Remember to push past 100% before an Occupation Battle. And never let your tickets sit at five.

The regions beyond are waiting. Claim them.

Do this guide cover what you want to know? If you want to ask more question, look for team formations (in multiplayer games), challenge other players, and exchange information, you can go on gaming forum (click here).