# Furnace & City

Source page: https://wos.sheet.guide/en/guides/furnace  
Last checked: 17 Oct 2026  
Unofficial fan site, not affiliated with Century Games. Numbers, unlock days and event rules change with patches and differ between states; treat them as rules of thumb and confirm in-game.

The Furnace gates almost everything: building levels, troop tiers and new features.

**TL;DR:** Push the Furnace first. Build only the prerequisites its next level asks for, plus the Research Center and troop camps.

## At a glance

### At a glance

- **Furnace** first. Check what its next level requires and build that.
- Then the **Research Center** and your **troop camps**.
- Use your **second queue** for prerequisites, camps and the Embassy.
- After **Furnace 30**, Fire Crystals take over. Bank them from events beforehand.

## Details

### Build priorities

- **Furnace** first. Check the next level’s requirements early and start those prerequisites on your second queue so they’re ready when it finishes.
- **Research Center:** upgrade it when its level blocks research you want, and keep it busy.
- **Infantry, Lancer and Marksman camps** are upgraded separately. Raise them to match the troop tier you want.
- **Embassy:** keep it near your Furnace level. It gives Alliance Assists and reinforcement capacity.
- **Infirmary** before big PvP events; the **Command Center** if you lead rallies.
- Resource buildings are filler. Upgrade them when a queue would sit idle, a prerequisite needs them, or you’re short of a resource.
- The **second construction queue** is a one-time store pack. It only pays off if you can keep both queues busy.

### Fire Crystal era (after Furnace 30)

| Stage | What changes | Tip |
| --- | --- | --- |
| Entry | **Furnace 30**, plus a server that has reached its first Fire Crystal Age (around server day 60) | Bank Fire Crystals from events before it opens so you can climb fast. |
| FC1 – FC10 | The Furnace climbs through sub-levels (FC1-1, FC1-2…). Camps and other buildings have FC prerequisites too. | Check which camp the next Furnace step needs before you spend. |
| Refined Fire Crystals | Start showing up in building costs around **FC6–FC8**. The **Crystal Laboratory** (around FC4–5) refines them. | Refining is rate-limited, so start early and keep it running. |
| War Academy | Needs **FC5**. Unlocks **T11 Helios** troop research, then **T12 Exalted and Molten** research (added in 2026). | Helios research is paid in **Fire Crystal Shards**, which have a daily cap. |

Note: Exact Fire Crystal costs differ between sources and change with patches. Check the in-game requirements.

### Survivors & weather

- Keep survivors **warm, fed and healthy**. The furnace burns **coal**, and a cold city makes survivors sick.
- **Blizzards** are server-wide cold snaps that test your heat. Top up coal and furnace output before you log off.
- Assign workers to the production you are short on.