Threats
Infiltrators & Echo Signals - Remnants: Post-Collapse Idle Survival
Infiltrators
Once the Defense panel unlocks, your perimeter faces a second threat alongside scheduled Raids: Infiltrators. These are enemy scavengers who slip through the wire between raids and quietly drain your resources while they're inside the compound.
- Spawn timing: after a 5-minute grace period from unlocking Defense, Infiltrators spawn on a random 4.2-11.2 minute timer.
- Group size: each spawn brings 1-2 Infiltrators, up to a hard cap of 2 active at once.
- Drain rate: while active, each Infiltrator drains 3% of your current production rate per tick across scrap, food, water, tech, and influence.
- Escape window: an Infiltrator that isn't repelled within 5 minutes escapes with everything it drained - permanently lost.
Reducing Spawn Chance
| Building | Effect |
|---|---|
| 🔦 Floodlights | −20% spawn chance per Floodlight |
| 🏚 Guard Barracks (Lv.3+) | An additional flat −20% spawn chance |
| Combined cap | Spawn chance reduction caps at 80% |
Signal Intelligence research also reduces the drain rate per Infiltrator (separate from spawn chance), making each breach less costly even if you can't prevent it entirely.
Repelling Infiltrators
Each active Infiltrator gets its own slot in the Defense panel showing a countdown bar and the running total drained so far. Click Repel to clear it.
- Recovery rate: repelling returns 1.15× everything that Infiltrator drained - you come out ahead on the resources it took.
- Bonus loot: on top of the recovery, you receive a flat scrap bonus equal to 30 seconds of your current scrap production.
- No cost or risk: repelling is a single click with no downside - there's never a reason not to repel as soon as you notice the alert.
Echo Signal Events
Echo Signals are short, clickable random events - the active-play counterpart to Infiltrators' passive threat. A signal spawns on a random 3-10 minute timer (faster with the Signal Intelligence Forge upgrade) and gives you a 15-second window to click it before it expires unclaimed.
- Unlock: signals begin once your shelter reaches level 1.
- Indicator: a pulsing signal icon appears in the UI with a countdown when active.
- Missed signals: if the 15-second window expires, the signal is lost - tracked as a missed signal, no penalty beyond the missed reward.
Signal Types
| Signal | Effect | Notes |
|---|---|---|
| 📦 Supply Drop | 2× all production for 90 seconds | Always eligible |
| 💰 Wandering Cache | Instant scrap = 6 minutes of current production | Always eligible |
| 👥 Survivor Wave | Up to 15 survivors join (capped by population cap) | Requires Population unlocked |
| 🛡 Raider Retreat | Next raid delayed 8 minutes | Requires Defense unlocked |
| ◈ Echo Pulse | +1 Echo Fragment (runs 1-2), +2 (run 3+) | Requires at least 1 Echo Reset |
| ⚡ Tech Surge | 5× tech generation for 60 seconds | Always eligible |
Which signal spawns is weighted-random among the types currently eligible for your save. Echo Pulse only appears after your first Echo Reset, tying this system directly into the Echo Fragment economy and the Echo Cascade run-10 milestone, which rewards intercepting 3 signals in a single run.
Strategy
- Keep a tab open during active play. The 15-second Echo Signal window is tight - if you're tabbed away, you'll miss most of them.
- Build Floodlights and Guard Barracks early. Both reduce Infiltrator spawn frequency, and Floodlights also help with raid defense.
- Repel on sight. There's no reason to delay - the 1.15× recovery plus scrap bonus makes every repel a net gain.
- Push toward run 10 for Echo Cascade. Once Forge upgrades reduce the Echo Signal interval, intercepting 3 signals per run for the Echo Cascade bonus becomes routine.
Also see: Raid Defense → · Echo Reset → · Wiki Hub →
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