diff --git a/GameEngine/Artifacts.php b/GameEngine/Artifacts.php
index ecbf6d0c..6e4a8c9d 100644
--- a/GameEngine/Artifacts.php
+++ b/GameEngine/Artifacts.php
@@ -277,39 +277,58 @@ class Artifacts
         global $database;
         
         //Register the Natars account, the Natars' password is the same as the MH's one
+        //NOTE: pre-existing anomaly, left untouched - this call passes 8 args
+        //(...,  self::NATARS_DESC, self::NATARS_DESC2) but register() only
+        //accepts up to $desc (7 params), so NATARS_DESC2 is silently dropped
+        //by PHP. Not related to the crash fixed below.
         $password = $database->getUserField(5, 'password', 0);
         $database->register(TRIBE5, $password, self::NATARS_EMAIL, self::NATARS_TRIBE, null, self::NATARS_UID, self::NATARS_DESC, self::NATARS_DESC2);
-        
-        //Convert from coordinates to village IDs
-        $possibleWids = $database->getVilWrefs(self::NATARS_CAPITAL_COORDINATES);
-        
-        //Check if the villages aren't already taken
-        $wid = $database->getFreeVillage($possibleWids);
 
-        //Generate the Natars' capital
-        //
-		// The capital starts with the World Wonder and the infrastructure defined
-		// in NATARS_CAPITAL_BUILDINGS. The data is passed in the same format used
-		// for World Wonder villages: [0] = column names, [1][] = values.
-        $capitalBuildings = [];
-        $capitalBuildings[0]   = array_keys(self::NATARS_CAPITAL_BUILDINGS);
-        $capitalBuildings[1][] = array_values(self::NATARS_CAPITAL_BUILDINGS);
+        //Idempotency guard: this whole method isn't wrapped in a transaction,
+        //so a previous run may have already built the Natars' capital (e.g.
+        //the register() call above went through, then the process died/timed
+        //out before finishing). Reuse the existing capital instead of trying
+        //to generate a second one, which would either collide or leave a
+        //stray village behind.
+        $existingCapital = $database->getVrefCapital(self::NATARS_UID);
+        if ($existingCapital) {
+            $wid = $existingCapital['wref'];
+        } else {
+            //Convert from coordinates to village IDs
+            $possibleWids = $database->getVilWrefs(self::NATARS_CAPITAL_COORDINATES);
 
-		// The capital army, using the same format as World Wonder villages:
-		// [0] = column names, [1][] = values.
-        $capitalUnits = [];
-        $capitalUnits[0]   = array_keys(self::NATARS_CAPITAL_UNITS);
-        $capitalUnits[1][] = array_values(self::NATARS_CAPITAL_UNITS);
+            //Check if the villages aren't already taken
+            $wid = $database->getFreeVillage($possibleWids);
 
-        $wid = $database->generateVillages(
-            [['wid' => $wid, 'mode' => 2, 'type' => 3, 'kid' => 0, 'capital' => 1, 'pop' => 1163, 'name' => null, 'natar' => 0]],
-            self::NATARS_UID,
-            TRIBE5,
-            $capitalUnits,
-            $capitalBuildings
-        );
+            //Generate the Natars' capital
+            //
+            // The capital starts with the World Wonder and the infrastructure defined
+            // in NATARS_CAPITAL_BUILDINGS. The data is passed in the same format used
+            // for World Wonder villages: [0] = column names, [1][] = values.
+            $capitalBuildings = [];
+            $capitalBuildings[0]   = array_keys(self::NATARS_CAPITAL_BUILDINGS);
+            $capitalBuildings[1][] = array_values(self::NATARS_CAPITAL_BUILDINGS);
+
+            // The capital army, using the same format as World Wonder villages:
+            // [0] = column names, [1][] = values.
+            $capitalUnits = [];
+            $capitalUnits[0]   = array_keys(self::NATARS_CAPITAL_UNITS);
+            $capitalUnits[1][] = array_values(self::NATARS_CAPITAL_UNITS);
+
+            $wid = $database->generateVillages(
+                [['wid' => $wid, 'mode' => 2, 'type' => 3, 'kid' => 0, 'capital' => 1, 'pop' => 1163, 'name' => null, 'natar' => 0]],
+                self::NATARS_UID,
+                TRIBE5,
+                $capitalUnits,
+                $capitalBuildings
+            );
+        }
 
         //Scouts all players
+        //NOTE: if this retry path is taken (capital already existed), players
+        //get scouted again - harmless duplicate espionage reports, not data
+        //corruption. Only reachable if a prior run died after building the
+        //capital but before finishing artifact spawning below.
         $this->scoutAllPlayers($wid);
         
         //Add artifacts
diff --git a/GameEngine/Database/DatabaseUserQueries.php b/GameEngine/Database/DatabaseUserQueries.php
index 682ec037..2ced213f 100644
--- a/GameEngine/Database/DatabaseUserQueries.php
+++ b/GameEngine/Database/DatabaseUserQueries.php
@@ -31,6 +31,27 @@ trait DatabaseUserQueries {
     $time = time();
     $access = USER;
 
+    // Idempotency guard for pre-assigned IDs (system accounts such as
+    // Natars, uid=3, called from Artifacts::createNatars()). Regular
+    // player registration always passes uid=0, so this branch never
+    // runs for it. It exists because createNatars() is not wrapped in
+    // a transaction: if it registers the Natars row but then dies
+    // further down (village/scout/artifact generation), every retry
+    // used to hit this INSERT again and throw an uncaught
+    // "Duplicate entry '3' for key PRIMARY" mysqli_sql_exception,
+    // fatal on every cron tick and page-load fallback. Detect the
+    // existing row and hand its id back instead of re-inserting.
+    if ($uid > 0) {
+        $existing = $this->dblink->prepare("SELECT id FROM `".TB_PREFIX."users` WHERE id = ? LIMIT 1");
+        $existing->bind_param("i", $uid);
+        $existing->execute();
+        $existingRow = $existing->get_result()->fetch_assoc();
+        $existing->close();
+        if ($existingRow) {
+            return (int)$existingRow['id'];
+        }
+    }
+
     // New accounts inherit the configured server language.
     // English remains the safe fallback if SERVER_LANG is missing or invalid.
     $serverLang = defined('SERVER_LANG')
@@ -902,4 +923,4 @@ trait DatabaseUserQueries {
     }
     return empty($errors) ? true : $errors;
 	}
-}
+}
\ No newline at end of file
diff --git a/install/data/constant_format.tpl b/install/data/constant_format.tpl
index 75430e2d..392bfd95 100644
--- a/install/data/constant_format.tpl
+++ b/install/data/constant_format.tpl
@@ -120,7 +120,7 @@ define("START_TIME", "%SSTARTTIME%");
 // SERVER_LANG is the DEFAULT language of the server (chosen at install / in
 // the admin "Server Settings"). LANG is the EFFECTIVE display language.
 //
-// Per-user language (issue #166): if the logged-in player picked a language
+// Per-user language : if the logged-in player picked a language
 // in their profile preferences (stored in users.lang and mirrored into
 // $_SESSION['lang']), LANG becomes that language; otherwise LANG falls back
 // to SERVER_LANG.