diff --git a/api/src/main/kotlin/br/com/gamemods/minecity/api/MineCity.kt b/api/src/main/kotlin/br/com/gamemods/minecity/api/MineCity.kt
index 6468400..1b17c39 100644
--- a/api/src/main/kotlin/br/com/gamemods/minecity/api/MineCity.kt
+++ b/api/src/main/kotlin/br/com/gamemods/minecity/api/MineCity.kt
@@ -1,10 +1,10 @@
 package br.com.gamemods.minecity.api
 
 import br.com.gamemods.minecity.api.annotation.internal.InternalMineCityApi
+import br.com.gamemods.minecity.api.service.MineCityInternal
 import br.com.gamemods.minecity.api.service.namedplayer.NamedPlayerService
 import br.com.gamemods.minecity.api.service.permission.PermissionService
 
-private lateinit var currentInstance: MineCity
 
 /**
  * Interface that allows other mods to interact with MineCity.
@@ -27,16 +27,8 @@ public interface MineCity {
 
     /**
      * This companion object allows MineCity interface to be used directly in kotlin delegating all API calls to
-     * the instance that is set at [instance].
-     *
-     * @property instance Access to the MineCity API implementation, must be modified only by MineCity itself, can be accessed freely.
+     * the instance that is set at [MineCityInternal.implementation].
      */
-    public companion object: MineCity by currentInstance {
-        public var instance: MineCity
-            get() = currentInstance
-            @InternalMineCityApi
-            set(value) {
-                currentInstance = value
-            }
-    }
+    @OptIn(InternalMineCityApi::class)
+    public companion object: MineCity by MineCityInternal.implementation
 }
diff --git a/api/src/main/kotlin/br/com/gamemods/minecity/api/id/ClaimPermissionId.kt b/api/src/main/kotlin/br/com/gamemods/minecity/api/id/ClaimPermissionId.kt
index 25e3c0f..1591daf 100644
--- a/api/src/main/kotlin/br/com/gamemods/minecity/api/id/ClaimPermissionId.kt
+++ b/api/src/main/kotlin/br/com/gamemods/minecity/api/id/ClaimPermissionId.kt
@@ -31,7 +31,7 @@ public value class ClaimPermissionId(private val id: String) {
         /**
          * The regex pattern that valid ClaimPermissionId instances must match.
          */
-        private val VALID_REGEX = Regex("^([a-z][a-z0-9]*)(_[a-z][a-z0-9]*)*:/([a-z][a-z0-9]*)(_[a-z][a-z0-9]*)*$")
+        private val VALID_REGEX = Regex("^([a-z][a-z0-9]*)(_[a-z][a-z0-9]*)*:([a-z][a-z0-9]*)(_[a-z][a-z0-9]*)*$")
 
         /**
          * ClaimPermissionId instance for door-related permissions.
diff --git a/api/src/main/kotlin/br/com/gamemods/minecity/api/service/MineCityInternal.kt b/api/src/main/kotlin/br/com/gamemods/minecity/api/service/MineCityInternal.kt
new file mode 100644
index 0000000..2c3d9f4
--- /dev/null
+++ b/api/src/main/kotlin/br/com/gamemods/minecity/api/service/MineCityInternal.kt
@@ -0,0 +1,15 @@
+package br.com.gamemods.minecity.api.service
+
+import br.com.gamemods.minecity.api.MineCity
+import br.com.gamemods.minecity.api.annotation.internal.InternalMineCityApi
+
+/**
+ * Internal MineCity states and services, should not be used by API users.
+ */
+@InternalMineCityApi
+public object MineCityInternal {
+    /**
+     * Access to the MineCity API implementation, must be modified only by MineCity itself, can be accessed freely.
+     */
+    public lateinit var implementation: MineCity
+}
diff --git a/core/src/main/kotlin/br/com/gamemods/minecity/core/MineCityCore.kt b/core/src/main/kotlin/br/com/gamemods/minecity/core/MineCityCore.kt
index faee2b5..544fed9 100644
--- a/core/src/main/kotlin/br/com/gamemods/minecity/core/MineCityCore.kt
+++ b/core/src/main/kotlin/br/com/gamemods/minecity/core/MineCityCore.kt
@@ -5,6 +5,7 @@ import br.com.gamemods.minecity.api.MineCityPlatform
 import br.com.gamemods.minecity.api.annotation.internal.InternalMineCityApi
 import br.com.gamemods.minecity.api.annotation.side.ServerSideOnly
 import br.com.gamemods.minecity.api.service.namedplayer.NamedPlayerService
+import br.com.gamemods.minecity.api.service.permission.PermissionService
 import br.com.gamemods.minecity.core.service.world.WorldService
 import com.github.michaelbull.logging.InlineLogger
 
@@ -21,6 +22,7 @@ class MineCityCore(
     override val platform: MineCityPlatform,
     val worlds: WorldService,
     override val players: NamedPlayerService,
+    override val permission: PermissionService,
 ): MineCity {
 
     /**
diff --git a/core/src/main/kotlin/br/com/gamemods/minecity/core/service/permission/CorePermissionService.kt b/core/src/main/kotlin/br/com/gamemods/minecity/core/service/permission/CorePermissionService.kt
new file mode 100644
index 0000000..665bcbe
--- /dev/null
+++ b/core/src/main/kotlin/br/com/gamemods/minecity/core/service/permission/CorePermissionService.kt
@@ -0,0 +1,20 @@
+package br.com.gamemods.minecity.core.service.permission
+
+import br.com.gamemods.minecity.api.annotation.internal.InternalMineCityApi
+import br.com.gamemods.minecity.api.id.ClaimPermissionId
+import br.com.gamemods.minecity.api.service.permission.ClaimPermission
+import br.com.gamemods.minecity.api.service.permission.PermissionService
+
+@InternalMineCityApi
+class CorePermissionService: PermissionService {
+    private val permissions = mutableMapOf<ClaimPermissionId, ClaimPermission>()
+
+    override fun get(id: ClaimPermissionId): ClaimPermission = permissions[id] ?: error("Unknown permission $id")
+
+    override fun plusAssign(permission: ClaimPermission) {
+        permissions.compute(permission.id) { _, old ->
+            if(old == null) permission
+            else error("Permission ${permission.id} already registered")
+        }
+    }
+}
diff --git a/platform/fabric/src/main/kotlin/br/com/gamemods/minecity/fabric/MineCityFabric.kt b/platform/fabric/src/main/kotlin/br/com/gamemods/minecity/fabric/MineCityFabric.kt
index 03572e9..d6a783d 100644
--- a/platform/fabric/src/main/kotlin/br/com/gamemods/minecity/fabric/MineCityFabric.kt
+++ b/platform/fabric/src/main/kotlin/br/com/gamemods/minecity/fabric/MineCityFabric.kt
@@ -5,9 +5,11 @@ import br.com.gamemods.minecity.api.annotation.internal.InternalMineCityApi
 import br.com.gamemods.minecity.api.annotation.side.ServerSideOnly
 import br.com.gamemods.minecity.api.client.MineCityClient
 import br.com.gamemods.minecity.api.math.pos.*
+import br.com.gamemods.minecity.api.service.MineCityInternal
 import br.com.gamemods.minecity.core.MineCityCore
 import br.com.gamemods.minecity.core.dispatchers.Async
 import br.com.gamemods.minecity.core.dispatchers.Sync
+import br.com.gamemods.minecity.core.service.permission.CorePermissionService
 import br.com.gamemods.minecity.fabric.math.pos.FabricBlockLocation
 import br.com.gamemods.minecity.fabric.math.pos.FabricChunkLocation
 import br.com.gamemods.minecity.fabric.math.pos.FabricEntityLocation
@@ -25,6 +27,8 @@ import com.github.michaelbull.logging.InlineLogger
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.asCoroutineDispatcher
 import net.fabricmc.api.ModInitializer
+import net.fabricmc.fabric.api.event.lifecycle.v1.ServerChunkEvents
+import net.fabricmc.fabric.api.event.lifecycle.v1.ServerLifecycleEvents
 import net.minecraft.server.MinecraftServer
 import net.minecraft.server.world.ServerWorld
 import net.minecraft.world.chunk.WorldChunk
@@ -58,16 +62,16 @@ object MineCityFabric : ModInitializer, MineCityPlatform {
 			platform = this,
 			worlds = FabricWorldService(this),
 			players = FabricNamedPlayerService(this),
+			permission = CorePermissionService(),
 		)
-		//FIXME
-		/*MineCity.instance = core
+		MineCityInternal.implementation = core
 		core.onInitialize()
 		ServerLifecycleEvents.SERVER_STARTING.register(this::handleServerStarting)
 		ServerLifecycleEvents.SERVER_STARTED.register(this::handleServerStarted)
 		ServerLifecycleEvents.SERVER_STOPPING.register(this::handleServerStopping)
 		ServerLifecycleEvents.SERVER_STOPPED.register(this::handleServerStopped)
 		ServerChunkEvents.CHUNK_LOAD.register(this::handleChunkLoad)
-		ServerChunkEvents.CHUNK_UNLOAD.register(this::handleChunkUnload)*/
+		ServerChunkEvents.CHUNK_UNLOAD.register(this::handleChunkUnload)
 
 		registerPermissions()
 	}