diff --git a/sources/Unreal/MutatorsAPI/Events/Mutator_OnModifyLogin_Signal.uc b/sources/Unreal/MutatorsAPI/Events/Mutator_OnModifyLogin_Signal.uc
new file mode 100644
index 0000000..5c806cf
--- /dev/null
+++ b/sources/Unreal/MutatorsAPI/Events/Mutator_OnModifyLogin_Signal.uc
@@ -0,0 +1,38 @@
+/**
+ *  Signal class implementation for `MutatorAPI`'s `OnModifyLogin` signal.
+ *      Copyright 2022 Anton Tarasenko
+ *------------------------------------------------------------------------------
+ * This file is part of Acedia.
+ *
+ * Acedia is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * Acedia is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with Acedia.  If not, see <https://www.gnu.org/licenses/>.
+ */
+class Mutator_OnModifyLogin_Signal extends Signal;
+
+public final function Emit(out string portal, out string options)
+{
+    local Slot nextSlot;
+    StartIterating();
+    nextSlot = GetNextSlot();
+    while (nextSlot != none)
+    {
+        Mutator_OnModifyLogin_Slot(nextSlot).connect(portal, options);
+        nextSlot = GetNextSlot();
+    }
+    CleanEmptySlots();
+}
+
+defaultproperties
+{
+    relatedSlotClass = class'Mutator_OnModifyLogin_Slot'
+}
\ No newline at end of file
diff --git a/sources/Unreal/MutatorsAPI/Events/Mutator_OnModifyLogin_Slot.uc b/sources/Unreal/MutatorsAPI/Events/Mutator_OnModifyLogin_Slot.uc
new file mode 100644
index 0000000..6d92035
--- /dev/null
+++ b/sources/Unreal/MutatorsAPI/Events/Mutator_OnModifyLogin_Slot.uc
@@ -0,0 +1,40 @@
+/**
+ *  Slot class implementation for `MutatorAPI`'s `OnModifyLogin` signal.
+ *      Copyright 2022 Anton Tarasenko
+ *------------------------------------------------------------------------------
+ * This file is part of Acedia.
+ *
+ * Acedia is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * Acedia is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with Acedia.  If not, see <https://www.gnu.org/licenses/>.
+ */
+class Mutator_OnModifyLogin_Slot extends Slot;
+
+delegate connect(out string portal, out string options)
+{
+    DummyCall();
+}
+
+protected function Constructor()
+{
+    connect = none;
+}
+
+protected function Finalizer()
+{
+    super.Finalizer();
+    connect = none;
+}
+
+defaultproperties
+{
+}
\ No newline at end of file
diff --git a/sources/Unreal/MutatorsAPI/MutatorAPI.uc b/sources/Unreal/MutatorsAPI/MutatorAPI.uc
index 9906ce0..785482e 100644
--- a/sources/Unreal/MutatorsAPI/MutatorAPI.uc
+++ b/sources/Unreal/MutatorsAPI/MutatorAPI.uc
@@ -1,7 +1,7 @@
 /**
  *      Low-level API that provides set of utility methods for working with
  *  `Mutator`s.
- *      Copyright 2021 Anton Tarasenko
+ *      Copyright 2021 - 2022 Anton Tarasenko
  *------------------------------------------------------------------------------
  * This file is part of Acedia.
  *
@@ -48,8 +48,9 @@ class MutatorAPI extends AcediaObject;
  *      checks and not really used for anything once these checks are complete.
  *      Some [sources]
  *      (https://wiki.beyondunreal.com/Legacy:Chain_Of_Events_At_Level_Startup)
- *      indicate that it used to omit additional `GameInfo`'s relevancy checks,
- *      however does not to serve any function in Killing Floor.
+ *      indicate that it is used to omit additional `GameInfo`'s
+ *      relevancy checks, however it does not seem to serve any function in
+ *      Killing Floor.
  *      Mutators might repurpose it for their own uses, but I am not aware of
  *      any that do.
  *  @return `false` if you want `other` to be destroyed and `true` otherwise.
@@ -87,6 +88,31 @@ public final function Mutator_OnMutate_Slot OnMutate(
     return Mutator_OnMutate_Slot(signal.NewSlot(receiver));
 }
 
+/**
+ *  Called from the `GameInfo`'s `Login()` function. Allows mutators to change
+ *  any options before the `Login()` function processes them.
+ *
+ *  [Signature]
+ *  <slot>(out string portal, out string options)
+ *
+ *  @param  Portal  Likely intended purpose is to indicate which "portal" was
+ *      used to allow player to enter this level, but does not seem to be doing
+ *      much in Killing Floor.
+ *  @param  options Options parts of URL that describe players entering
+ *      the server. Example is something like: "?LAN?Class=Engine.Pawn?
+ *      Character=Lieutenant_Masterson?team=1?VAC=1?password=pass?Name=guy".
+ */
+/* SIGNAL */
+public final function Mutator_OnModifyLogin_Slot OnModifyLogin(
+    AcediaObject receiver)
+{
+    local Signal        signal;
+    local UnrealService service;
+    service = UnrealService(class'UnrealService'.static.Require());
+    signal = service.GetSignal(class'Mutator_OnModifyLogin_Signal');
+    return Mutator_OnModifyLogin_Slot(signal.NewSlot(receiver));
+}
+
 defaultproperties
 {
 }
\ No newline at end of file
diff --git a/sources/Unreal/UnrealService.uc b/sources/Unreal/UnrealService.uc
index 473f4a4..24e53f1 100644
--- a/sources/Unreal/UnrealService.uc
+++ b/sources/Unreal/UnrealService.uc
@@ -119,4 +119,5 @@ defaultproperties
     serviceSignals(10)  = (signalClass=class'Broadcast_OnHandleTextFor_Signal')
     serviceSignals(11)  = (signalClass=class'Mutator_OnCheckReplacement_Signal')
     serviceSignals(12)  = (signalClass=class'Mutator_OnMutate_Signal')
+    serviceSignals(13)  = (signalClass=class'Mutator_OnModifyLogin_Signal')
 }
\ No newline at end of file