diff --git a/.envrc b/.envrc
new file mode 100644
index 00000000..1d953f4b
--- /dev/null
+++ b/.envrc
@@ -0,0 +1 @@
+use nix
diff --git a/.github/workflows/publish_to_nexus.yml b/.github/workflows/publish_to_nexus.yml
index b8804c9f..23802499 100644
--- a/.github/workflows/publish_to_nexus.yml
+++ b/.github/workflows/publish_to_nexus.yml
@@ -17,11 +17,11 @@ jobs:
 
     steps:
       - uses: actions/checkout@v4
-      - name: Set up JDK 17
+      - name: Set up JDK
         uses: actions/setup-java@v4
         with:
           distribution: adopt
-          java-version: 17
+          java-version: 21
       - name: Build with Gradle
         run: ./gradlew --build-cache build
       - name: Test with Gradle
diff --git a/.github/workflows/verify.yml b/.github/workflows/verify.yml
index 83725607..b1d9c4e5 100644
--- a/.github/workflows/verify.yml
+++ b/.github/workflows/verify.yml
@@ -11,11 +11,11 @@ jobs:
 
     steps:
       - uses: actions/checkout@v4
-      - name: Set up JDK 17
+      - name: Set up JDK
         uses: actions/setup-java@v4
         with:
           distribution: adopt
-          java-version: 17
+          java-version: 21
       - name: Build with Gradle
         run: ./gradlew --build-cache build
       - name: Test with Gradle
diff --git a/.gitignore b/.gitignore
index 763a8a1c..1946f27e 100644
--- a/.gitignore
+++ b/.gitignore
@@ -33,3 +33,4 @@ dependency-reduced-pom.xml
 buildNumber.properties
 .mvn/timing.properties
 .mvn/wrapper/maven-wrapper.jar
+.direnv
diff --git a/BloodNight-core/.gitignore b/BloodNight-core/.gitignore
new file mode 100644
index 00000000..7e3b24e0
--- /dev/null
+++ b/BloodNight-core/.gitignore
@@ -0,0 +1 @@
+run/
diff --git a/BloodNight-core/build.gradle.kts b/BloodNight-core/build.gradle.kts
index e5a84776..ae3049cc 100644
--- a/BloodNight-core/build.gradle.kts
+++ b/BloodNight-core/build.gradle.kts
@@ -1,6 +1,7 @@
 plugins {
     alias(libs.plugins.shadow)
     alias(libs.plugins.pluginyml)
+    alias(libs.plugins.runpaper)
 }
 
 dependencies {
@@ -68,6 +69,10 @@ tasks {
         from(shadowJar)
         destinationDir = File(path.toString())
     }
+
+    runServer{
+        minecraftVersion("1.21.1")
+    }
 }
 
 bukkit {
diff --git a/BloodNight-core/src/main/java/de/eldoria/bloodnight/core/BloodNight.java b/BloodNight-core/src/main/java/de/eldoria/bloodnight/core/BloodNight.java
index d2d07e70..62290367 100644
--- a/BloodNight-core/src/main/java/de/eldoria/bloodnight/core/BloodNight.java
+++ b/BloodNight-core/src/main/java/de/eldoria/bloodnight/core/BloodNight.java
@@ -94,16 +94,17 @@ public void onPluginEnable(boolean reload) {
 
             configuration = new Configuration(this);
 
-            ILocalizer localizer = Localizer.create(this, "de_DE", "en_US", "es_ES", "tr", "zh_CN");
-
             Map<String, String> mobLocaleCodes = SpecialMobRegistry.getRegisteredMobs().stream()
                     .map(MobFactory::getMobName)
                     .collect(Collectors.toMap(
                             k -> "mob." + k,
                             k -> String.join(" ", k.split("(?<=.)(?=\\p{Lu})"))));
-            localizer.addLocaleCodes(mobLocaleCodes);
+            ILocalizer localizer = Localizer.builder(this, "de_DE")
+                    .setIncludedLocales("en_US", "es_ES", "tr", "zh_CN")
+                    .setUserLocale(p -> configuration.getGeneralSettings().language())
+                    .addLocaleCodes(mobLocaleCodes)
+                    .build();
 
-            localizer.setLocale(configuration.getGeneralSettings().language());
             MessageSender.builder(this)
                     .prefix(configuration.getGeneralSettings().prefix())
                     .messageColor(NamedTextColor.GREEN)
@@ -132,9 +133,9 @@ public void onPluginEnable(boolean reload) {
 
             if (configuration.getGeneralSettings().updateReminder()) {
                 Updater.lyna(LynaUpdateData.builder(this, 4)
-                        .notifyPermission(Permissions.Admin.RELOAD)
-                        .updateUrl("https://bn.discord.eldoria.de/")
-                        .notifyUpdate(true).build())
+                                .notifyPermission(Permissions.Admin.RELOAD)
+                                .updateUrl("https://bn.discord.eldoria.de/")
+                                .notifyUpdate(true).build())
                         .start();
             }
 
diff --git a/build.gradle.kts b/build.gradle.kts
index 9c11c1a9..13a9e4f5 100644
--- a/build.gradle.kts
+++ b/build.gradle.kts
@@ -38,7 +38,7 @@ subprojects {
         withSourcesJar()
         withJavadocJar()
         toolchain {
-            languageVersion.set(JavaLanguageVersion.of(17))
+            languageVersion.set(JavaLanguageVersion.of(21))
         }
     }
 
diff --git a/settings.gradle.kts b/settings.gradle.kts
index 69a8e8cf..bb8a7e2f 100644
--- a/settings.gradle.kts
+++ b/settings.gradle.kts
@@ -12,7 +12,7 @@ pluginManagement {
 dependencyResolutionManagement {
     versionCatalogs {
         create("libs") {
-            version("eldoutil", "2.1.5")
+            version("eldoutil", "2.1.6")
             library("eldoutil.core", "de.eldoria.util", "core").versionRef("eldoutil")
             library("eldoutil.updater", "de.eldoria.util", "updater").versionRef("eldoutil")
             library("eldoutil.messaging", "de.eldoria.util", "messaging").versionRef("eldoutil")
@@ -35,8 +35,9 @@ dependencyResolutionManagement {
 
             plugin("publishdata", "de.chojo.publishdata").version("1.2.5")
             plugin("spotless", "com.diffplug.spotless").version("6.25.0")
-            plugin("shadow", "io.github.goooler.shadow").version("8.1.8")
+            plugin("shadow", "com.gradleup.shadow").version("8.3.0")
             plugin("pluginyml", "net.minecrell.plugin-yml.bukkit").version("0.6.0")
+            plugin("runpaper", "xyz.jpenilla.run-paper").version("2.3.1")
         }
     }
 }
diff --git a/shell.nix b/shell.nix
new file mode 100644
index 00000000..e6613cbb
--- /dev/null
+++ b/shell.nix
@@ -0,0 +1,11 @@
+{ pkgs ? import <nixpkgs> {}, ... }:
+
+let
+jdk = pkgs.jdk21;
+gradle= pkgs.gradle.override { java = jdk; };
+in
+pkgs.mkShell
+{
+  packages = with pkgs; [jdk gradle];
+}
+