Godot 3d tutorial: https://docs.godotengine.org/en/stable/getting_started/first_3d_game/07.killing_player.html

mob.tscn

@@ -0,0 +1,24 @@
+[gd_scene load_steps=4 format=3 uid="uid://h2hapmuai55b"]
+
+[ext_resource type="Script" path="res://Mob.gd" id="1_fih7b"]
+[ext_resource type="PackedScene" uid="uid://gqs4tdvjq5vi" path="res://art/mob.glb" id="2_0f7cl"]
+
+[sub_resource type="BoxShape3D" id="BoxShape3D_vwmkp"]
+size = Vector3(2, 1, 2.5)
+
+[node name="Mob" type="CharacterBody3D" groups=["mob"]]
+collision_layer = 2
+collision_mask = 0
+script = ExtResource("1_fih7b")
+
+[node name="Pivot" type="Node3D" parent="."]
+
+[node name="Character" parent="Pivot" instance=ExtResource("2_0f7cl")]
+
+[node name="CollisionShape3D" type="CollisionShape3D" parent="."]
+shape = SubResource("BoxShape3D_vwmkp")
+
+[node name="VisibilityNotifier" type="VisibleOnScreenNotifier3D" parent="."]
+aabb = AABB(-1.5, -1, -2, 3, 2, 4)
+
+[connection signal="screen_exited" from="VisibilityNotifier" to="." method="_on_visibility_notifier_screen_exited"]