diff --git a/apps/participation/management/commands/setup_third_phase.py b/apps/participation/management/commands/setup_third_phase.py
new file mode 100644
index 0000000..cab873e
--- /dev/null
+++ b/apps/participation/management/commands/setup_third_phase.py
@@ -0,0 +1,42 @@
+from django.core.management import BaseCommand
+
+from corres2math.matrix import Matrix, RoomVisibility
+from participation.models import Participation
+
+
+class Command(BaseCommand):
+    def handle(self, *args, **options):
+        for participation in Participation.objects.filter(valid=True).all():
+            for i, question in enumerate(participation.questions.order_by("id").all()):
+                solution_author = participation.received_participation.team
+                alias = f"equipe-{solution_author.trigram.lower()}-question-{i}"
+                room_id = f"#{alias}:correspondances-maths.fr"
+                Matrix.create_room(
+                    visibility=RoomVisibility.public,
+                    alias=alias,
+                    name=f"Solution équipe {solution_author.trigram} - question {i+1}",
+                    topic=f"Échange entre l'équipe {solution_author.name} ({solution_author.trigram}) "
+                          f"et l'équipe {participation.team.name} ({participation.team.trigram}) "
+                          f"autour de la question {i+1} sur le problème {participation.problem}",
+                    federate=False,
+                    invite=[f"@{registration.matrix_username}:correspondances-maths.fr" for registration in
+                            list(participation.team.students.all()) + list(participation.team.coachs.all()) +
+                            list(solution_author.students.all()) + list(solution_author.coachs.all())],
+                )
+                Matrix.set_room_power_level_event(room_id, "events_default", 21)
+                for registration in solution_author.students.all():
+                    Matrix.set_room_power_level(room_id,
+                                                f"@{registration.matrix_username}:correspondances-maths.fr", 42)
+
+                Matrix.send_message(room_id, "Bienvenue dans la troisième phase des Correspondances !")
+                Matrix.send_message(room_id, f"L'équipe {participation.team.name} a visionné la vidéo de l'équipe "
+                                    f"{solution_author.name} sur le problème {participation.problem}, et a posé "
+                                    "une série de questions.")
+                Matrix.send_message(room_id, "L'équipe ayant composé la vidéo doit maintenant proposer une réponse.")
+                Matrix.send_message(room_id, "Une fois la réponse apportée, vous pourrez ensuite échanger plus "
+                                             "librement autour de la question, au travers de ce canal.")
+                Matrix.send_message(room_id, "**Question posée :**", formatted_body="<strong>Question posée :</strong>")
+                Matrix.send_message(room_id, question.question,
+                                    formatted_body=f"<font color=\"#ff0000\">{question.question}</font>")
+
+                # TODO Setup the bot the set the power level of all members of the room to 42
diff --git a/corres2math/matrix.py b/corres2math/matrix.py
index 1f340d8..ddf76c6 100644
--- a/corres2math/matrix.py
+++ b/corres2math/matrix.py
@@ -238,6 +238,29 @@ class Matrix:
             room_id = await cls.resolve_room_alias(room_id)
         return await client.room_invite(room_id, user_id)
 
+    @classmethod
+    @async_to_sync
+    async def send_message(cls, room_id: str, body: str, formatted_body: str = None,
+                           msgtype: str = "m.text", html: bool = True):
+        """
+        Send a message to a room.
+        """
+        client = await cls._get_client()
+        if room_id.startswith("#"):
+            room_id = await cls.resolve_room_alias(room_id)
+        content = {
+                "msgtype": msgtype,
+                "body": body,
+                "formatted_body": formatted_body or body,
+        }
+        if html:
+            content["format"] = "org.matrix.custom.html"
+        return await client.room_send(
+            room_id=room_id,
+            message_type="m.room.message",
+            content=content,
+        )
+
     @classmethod
     @async_to_sync
     async def kick(cls, room_id: str, user_id: str, reason: str = None) -> Union[RoomKickResponse, RoomInviteError]: