diff --git a/application/src/Controller/MatrixController.php b/application/src/Controller/MatrixController.php
index 2bfb66d..92bf4f7 100644
--- a/application/src/Controller/MatrixController.php
+++ b/application/src/Controller/MatrixController.php
@@ -7,9 +7,9 @@
 use App\Entity\RoomMember;
 use App\Entity\Token;
 use App\Entity\User;
+use App\Service\Filter;
 use App\Traits\GeneralTrait;
 use App\Traits\MatrixSynapseTrait;
-use stdClass;
 use Symfony\Bundle\FrameworkBundle\Controller\AbstractController;
 use Symfony\Component\HttpFoundation\JsonResponse;
 use Symfony\Component\Routing\Annotation\Route;
@@ -273,6 +273,51 @@ public function createRoom(string $serverID, Request $request):JsonResponse {
         return new JsonResponse((object) $response, 200);
     }
 
+    /**
+     * Sync Matrix room.
+     * Sync room according to the API:
+     * https://spec.matrix.org/v1.8/client-server-api/#get_matrixclientv3sync
+     *
+     * @Route("/v3/sync")
+     * @param string $serverID
+     * @param Request $request
+     * @return JsonResponse
+     */
+    public function sync(string $serverID, Request $request):JsonResponse {
+        // 1. Check call auth.
+        // 2. Check HTTP method is accepted.
+        $accessCheck = $this->authHttpCheck(['GET'], $request);
+        if (!$accessCheck['status']) {
+            return $accessCheck['message'];
+        }
+        // Params are being queried via a filter in the request.
+        $filter = Filter::fromRequest($request);
+
+        $roomSearch = [
+            'serverid' => $serverID,
+        ];
+
+        if ($roomIds = $filter->getRoomFilter()->getRoomIds()) {
+            $roomSearch['roomid'] = $roomIds;
+        }
+
+        // Get a list of rooms.
+        $entityManager = $this->getDoctrine()->getManager();
+        $roomList = $entityManager->getRepository(Room::class)->findBy($roomSearch);
+
+        // Get room state data for each room.
+        $roomData = [];
+        foreach ($roomList as $room) {
+            $roomData[$room->getRoomId()] = $room->getRoomState($request);
+        }
+
+        return new JsonResponse((object) [
+            'rooms' => [
+                'join' => $roomData,
+            ],
+        ]);
+    }
+
     /**
      * Create Matrix room.
      *
@@ -402,6 +447,25 @@ public function roomState(string $serverID, string $roomID, string $eventType, R
             if (!$check['status']) {
                 return $check['message'];
             }
+            // Update power levels for each room member.
+            foreach ($payload->users as $userid => $level) {
+                if (!empty($level)) {
+                    $user = $entityManager->getRepository(User::class)->findOneBy([
+                        'serverid' => $serverID,
+                        'userid' => $userid,
+                    ]);
+                    if (!empty($user)) {
+                        $membership = $entityManager->getRepository(RoomMember::class)->findOneBy([
+                            'serverid' => $serverID,
+                            'room' => $room,
+                            'user' => $user,
+                        ]);
+                        if(!empty($membership)) {
+                            $membership->setPowerLevel($level);
+                        }
+                    }
+                }
+            }
         } else {
             // Unknown state.
             return new JsonResponse((object) [
diff --git a/application/src/Entity/Room.php b/application/src/Entity/Room.php
index f00d1f5..25b173b 100644
--- a/application/src/Entity/Room.php
+++ b/application/src/Entity/Room.php
@@ -200,4 +200,62 @@ public function getMembers(): Collection
     {
         return $this->members;
     }
+
+    public function getRoomState(): array
+    {
+        // We will probably need to pass a filter in the future.
+        // At the moment we only know how to serve a set of power levels.
+        $roomData = [
+            'state' => [
+                'events' => [],
+            ],
+        ];
+
+        $roomData['state']['events'][] = $this->getPowerLevelState();
+
+        return $roomData;
+    }
+
+    protected function getPowerLevelState(): array
+    {
+        // Power level values.
+        $powerLevelDefault = 0;
+        $powerLevelModerator = 50;
+        $powerLevelMaximum = 100;
+
+        // Get the members of the room who have a powerlevel set.
+        $members = $this->getMembers()->filter(function (RoomMember $member) {
+            return $member->getPowerLevel() !== null;
+        });
+
+        // Build the power level state.
+        $memberInfo = $members->map(fn(RoomMember $member) => [
+            $member->getUser()->getUserid() => $member->getPowerLevel(),
+        ])->toArray();
+
+        return [
+            'type' => 'm.room.power_levels',
+            'content' => [
+                'users' => (object) $memberInfo,
+                'users_default' => $powerLevelDefault,
+                'events' => [
+                    'm.room.name' => $powerLevelModerator,
+                    'm.room.power_levels' => $powerLevelMaximum,
+                    'm.room.history_visibility' => $powerLevelMaximum,
+                    'm.room.canonical_alias' => $powerLevelModerator,
+                    'm.room.avatar' => $powerLevelModerator,
+                    'm.room.tombstone' => $powerLevelMaximum,
+                    'm.room.server_acl' => $powerLevelMaximum,
+                    'm.room.encryption' => $powerLevelMaximum,
+                ],
+                'events_default' =>  $powerLevelDefault,
+                'state_default' => $powerLevelModerator,
+                'ban' => $powerLevelModerator,
+                'kick' => $powerLevelModerator,
+                'redact' => $powerLevelModerator,
+                'invite' =>  $powerLevelDefault,
+                'historical' => $powerLevelMaximum,
+            ],
+        ];
+    }
 }
diff --git a/application/src/Entity/RoomMember.php b/application/src/Entity/RoomMember.php
index 32e26fa..54f862c 100644
--- a/application/src/Entity/RoomMember.php
+++ b/application/src/Entity/RoomMember.php
@@ -56,6 +56,11 @@ class RoomMember
      */
     private $state;
 
+    /**
+     * @ORM\Column(type="integer", nullable=true)
+     */
+    private $powerlevel;
+
     public function getId(): ?int
     {
         return $this->id;
@@ -154,4 +159,16 @@ public function setState(string $state = null): self
 
         return $this;
     }
+
+    public function getPowerLevel(): ?int
+    {
+        return $this->powerlevel;
+    }
+
+    public function setPowerLevel(int $powerlevel): self
+    {
+        $this->powerlevel = $powerlevel;
+
+        return $this;
+    }
 }
diff --git a/application/src/Service/Filter.php b/application/src/Service/Filter.php
new file mode 100644
index 0000000..f69cb96
--- /dev/null
+++ b/application/src/Service/Filter.php
@@ -0,0 +1,55 @@
+<?php
+
+namespace App\Service;
+
+use App\Service\Filter\RoomFilter;
+use Symfony\Component\HttpFoundation\Request;
+
+
+class Filter
+{
+    private array $roomIds = [];
+    private RoomFilter $roomFilter;
+
+    public static function fromRequest(Request $request): static
+    {
+        $filter = new static();
+
+        $filterData = $request->query->get('filter');
+        if (!$filterData) {
+            return $filter;
+        }
+
+        // Filter the event data according to the API:
+        // https://spec.matrix.org/v1.1/client-server-api/#filtering
+        // Filters are made up of different filter types.
+        // Detailed here: https://spec.matrix.org/v1.1/client-server-api/#post_matrixclientv3useruseridfilter
+        $filterData = json_decode($request->query->get('filter'));
+
+        if (property_exists($filterData, 'room')) {
+            $filter->setRoomFilter(RoomFilter::fromObject($filterData->room));
+        }
+
+        return $filter;
+    }
+
+    public function setRoomFilter(RoomFilter $roomFilter): static
+    {
+        $this->roomFilter = $roomFilter;
+        return $this;
+    }
+
+    public function getRequestedRoomIds(): array
+    {
+        return $this->roomIds;
+    }
+
+    public function getRoomFilter(): RoomFilter
+    {
+        if (empty($this->roomFilter)) {
+            $this->roomFilter = new RoomFilter();
+        }
+
+        return $this->roomFilter;
+    }
+}
diff --git a/application/src/Service/RoomFilter.php b/application/src/Service/RoomFilter.php
new file mode 100644
index 0000000..6758fd9
--- /dev/null
+++ b/application/src/Service/RoomFilter.php
@@ -0,0 +1,49 @@
+<?php
+
+namespace App\Service\Filter;
+
+class RoomFilter
+{
+    private array $roomIds = [];
+    private StateFilter $roomStateFilter;
+
+    public static function fromObject(\stdClass $filterData): static
+    {
+        $filter = new static();
+
+        // Check for a list of rooms.
+        if (property_exists($filterData, 'rooms')) {
+            $rooms = (array) $filterData->rooms;
+            $filter->setRoomIds($rooms);
+        }
+
+        // Check for a room state filter.
+        if (property_exists($filterData, 'state')) {
+            $filter->setRoomState(StateFilter::fromObject($filterData->state));
+        }
+
+        return $filter;
+    }
+
+    public function setRoomIds(array $ids): static
+    {
+        $this->roomIds = $ids;
+        return $this;
+    }
+
+    public function setRoomState(StateFilter $state): static
+    {
+        $this->roomStateFilter = $state;
+        return $this;
+    }
+
+    public function getRoomIds(): array
+    {
+        return $this->roomIds;
+    }
+
+    public function getRoomState(): StateFilter
+    {
+        return $this->roomStateFilter;
+    }
+}
diff --git a/application/src/Service/StateFilter.php b/application/src/Service/StateFilter.php
new file mode 100644
index 0000000..d8b9220
--- /dev/null
+++ b/application/src/Service/StateFilter.php
@@ -0,0 +1,32 @@
+<?php
+
+namespace App\Service\Filter;
+
+class StateFilter
+{
+    private array $types = [];
+
+    public static function fromObject(\stdClass $filterData): static
+    {
+        $filter = new static();
+
+        // We currently only support types.
+        if (property_exists($filterData, 'types')) {
+            $types = (array) $filterData->types;
+            $filter->setTypes($types);
+        }
+
+        return $filter;
+    }
+
+    public function setTypes(array $types): static
+    {
+        $this->types = $types;
+        return $this;
+    }
+
+    public function getTypes(): array
+    {
+        return $this->types;
+    }
+}