diff --git a/src/EventContext.php b/src/EventContext.php
index 7f757ea..faa3708 100644
--- a/src/EventContext.php
+++ b/src/EventContext.php
@@ -20,12 +20,12 @@ class EventContext
      * EventContext constructor.
      * @param string $event The published event
      * @param string $matchingPattern The matching pattern
-     * @param array $data
+     * @param EventContextDataContainer $data
      */
     public function __construct(
         string $event,
         string $matchingPattern,
-        array $data
+        EventContextDataContainer $data
     ) {
         $this->event = $event;
         $this->matchingPattern = $matchingPattern;
@@ -51,102 +51,40 @@ class EventContext
     }
 
     /**
-     * Returns a list of fields in this context
-     * @return array
+     * Returns the immutable data container.
+     * @return EventContextDataContainer
      */
-    public function getListOfFields(): array
+    public function getData(): EventContextDataContainer
     {
-        return array_keys($this->data);
+        return $this->data;
     }
 
     /**
-     * Returns a comma separated string with all allowed fields, for debugging reasons.
-     * @return string
-     */
-    private function getFormattedListOfFields(): string
-    {
-        return substr(
-            implode(", ", $this->getListOfFields()),
-            0,
-            -2
-        );
-    }
-
-    /**
-     * Sets a field and returns the changed object.
-     * @param $field
-     * @param $value
-     * @return EventContext
-     */
-    public function setField($field, $value): self
-    {
-        if ($this->hasField($field)) {
-            $data = $this->data;
-            $data[$field] = $value;
-        } else {
-            $this->throwException($field);
-        }
-
-        return new static($this->event, $this->matchingPattern, $data);
-    }
-
-    /**
-     * Sets multiple fields at once and returns the changed object.
-     * @param $data array of field => value
-     * @return EventContext
-     */
-    public function setFields($data): self
-    {
-        $oldData = $this->data;
-
-        foreach ($data as $key => $value) {
-            if ($this->hasField($field)) {
-                $oldData[$key] = $value;
-            } else {
-                $this->throwException($field);
-            }
-        }
-
-        return new static($this->event, $this->matchingPattern, $oldData);
-    }
-
-    /**
-     * Returns the data to a field.
+     * Returns a data field
      * @param $field
      * @return mixed
      */
-    public function getField($field)
+    public function getDataField($field)
     {
-        if ($this->hasField($field)) {
-            return $this->data[$field];
-        } else {
-            $this->throwException($field);
-        }
+        return $this->data->get($field);
     }
 
     /**
-     * Returns true if the context has a specific field.
+     * Sets a data field
      * @param $field
-     * @return bool
+     * @param $value
      */
-    public function hasField($field)
+    public function setDataField($field, $value)
     {
-        if (isset($this->data[$field])) {
-            return true;
-        } else {
-            return false;
-        }
+        $this->data = $this->data->set($field, $value);
     }
 
     /**
-     * internal use only - throws an ArgumentException a field is given that's not valid.
-     * @param $field
-     * @throws ArgumentException
+     * Sets multiple data fields at once.
+     * @param $data
      */
-    private function throwException($field)
+    public function setDataFields($data)
     {
-        throw new ArgumentException(
-            "{$field} is not valid in this context, only {$this->getFormattedListOfFields()} are allowed."
-        );
+        $this->data = $this->data->setFields($data);
     }
 }
\ No newline at end of file
diff --git a/src/EventContextDataContainer.php b/src/EventContextDataContainer.php
new file mode 100644
index 0000000..5b81107
--- /dev/null
+++ b/src/EventContextDataContainer.php
@@ -0,0 +1,130 @@
+<?php
+declare(strict_types=1);
+
+namespace LotGD\Core;
+
+
+use LotGD\Core\Exceptions\ArgumentException;
+
+class EventContextDataContainer
+{
+    private $data;
+
+    /**
+     * Creates a new instance of a data container.
+     *
+     * Sub types can change this method to force certain parameters.
+     * @param array $data
+     * @return EventContextDataContainer
+     */
+    public static function create(array $data): self
+    {
+        return new static($data);
+    }
+
+    /**
+     * protected constructor..
+     * @see self::create
+     * @param array $data
+     */
+    protected function __construct(array $data)
+    {
+        $this->data = $data;
+    }
+
+    /**
+     * Returns true if container has a certain field.
+     * @param string $field
+     * @return bool
+     */
+    public function has(string $field): bool
+    {
+        return isset($this->data[$field]);
+    }
+
+    /**
+     * Returns the value of a field.
+     * @param string $field
+     * @return mixed
+     */
+    public function get(string $field)
+    {
+        if ($this->has($field)) {
+            return $this->data[$field];
+        } else {
+            $this->throwException($field);
+        }
+    }
+
+    /**
+     * Sets a field to a new value and returns a new data container
+     * @param string $field
+     * @param $value
+     * @return EventContextDataContainer
+     */
+    public function set(string $field, $value): self
+    {
+        if ($this->has($field)) {
+            $data = $this->data;
+            $data[$field] = $value;
+
+            return new static($data);
+        } else {
+            $this->throwException($field);
+        }
+    }
+
+    /**
+     * Sets multiple fields at once
+     * @param array $data array of $field=>$value pairs
+     * @return EventContextDataContainer
+     */
+    public function setFields(array $data): self
+    {
+        $data = $this->data;
+
+        foreach ($data as $field => $value) {
+            if ($this->has($field)) {
+                $data[$field] = $value;
+            } else {
+                $this->throwException($field);
+            }
+        }
+
+        return new static($data);
+    }
+
+    /**
+     * Returns a list of fields in this context
+     * @return array
+     */
+    private function getListOfFields(): array
+    {
+        return array_keys($this->data);
+    }
+
+    /**
+     * Returns a comma separated string with all allowed fields, for debugging reasons.
+     * @return string
+     */
+    private function getFormattedListOfFields(): string
+    {
+        return substr(
+            implode(", ", $this->getListOfFields()),
+            0,
+            -2
+        );
+    }
+
+    /**
+     * internal use only - throws an ArgumentException a field is given that's not valid.
+     * @param $field
+     * @throws ArgumentException
+     */
+    private function throwException($field)
+    {
+        throw new ArgumentException(
+            "{$field} is not valid in this context, only {$this->getFormattedListOfFields()} are allowed."
+        );
+    }
+}
\ No newline at end of file
diff --git a/src/EventHandler.php b/src/EventHandler.php
index 18c87e8..ffac91f 100644
--- a/src/EventHandler.php
+++ b/src/EventHandler.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace LotGD\Core;
 
@@ -14,5 +15,5 @@ interface EventHandler
      * the next handler is called. Otherwise, return null. Any changes made will be propogated
      * to the event publisher as well.
      */
-    public static function handleEvent(Game $g, string $event, array &$context);
+    public static function handleEvent(Game $g, EventContext $context): EventContext;
 }