diff --git a/asm/battle_intro.s b/asm/battle_intro.s
index 04a0301ce..f65bc3307 100644
--- a/asm/battle_intro.s
+++ b/asm/battle_intro.s
@@ -228,6 +228,9 @@ HandleIntroSlide: @ 81181D4
 	ldr r0, =0x00000c03
 	cmp r1, r0
 	beq _08118208
+	adds r0, r0, #1
+	cmp r1, r0
+	bhi _08118208
 	ldr r0, =sub_8118D68
 	b _08118258
 	.pool
diff --git a/data/maps/EverGrandeCity_PokemonLeague_1F/scripts.inc b/data/maps/EverGrandeCity_PokemonLeague_1F/scripts.inc
index b4046d022..4e46bd1d0 100644
--- a/data/maps/EverGrandeCity_PokemonLeague_1F/scripts.inc
+++ b/data/maps/EverGrandeCity_PokemonLeague_1F/scripts.inc
@@ -47,6 +47,11 @@ EverGrandeCity_PokemonLeague_1F_Pokemart_229624: @ 8229624
 	end
 
 EverGrandeCity_PokemonLeague_1F_EventScript_229636:: @ 8229636
+	setvar VAR_0x8004, 11
+	setvar VAR_0x8006, 404
+	setvar VAR_0x8007, 3
+	special DoSpecialTrainerBattle
+	waitstate
 	lockall
 	checkflag FLAG_0x107
 	goto_eq EverGrandeCity_PokemonLeague_1F_EventScript_2296BB
diff --git a/include/battle.h b/include/battle.h
index d25ee3a33..bbdc3a7a3 100644
--- a/include/battle.h
+++ b/include/battle.h
@@ -861,6 +861,7 @@ extern u8 gBattleMonForms[MAX_BATTLERS_COUNT];
 extern u32 gFieldStatuses;
 extern struct FieldTimer gFieldTimers;
 extern u8 gBattlerAbility;
+extern u16 gPartnerSpriteId;
 
 extern void (*gPreBattleCallback1)(void);
 extern void (*gBattleMainFunc)(void);
diff --git a/include/battle_setup.h b/include/battle_setup.h
index 88100cf4e..4e6f8ebe2 100644
--- a/include/battle_setup.h
+++ b/include/battle_setup.h
@@ -47,6 +47,7 @@ void BattleSetup_StartLegendaryBattle(void);
 void StartGroudonKyogreBattle(void);
 void StartRegiBattle(void);
 u8 BattleSetup_GetTerrainId(void);
+u8 GetTrainerBattleTransition(void);
 u8 sub_80B100C(s32 arg0);
 void ChooseStarter(void);
 void ResetTrainerOpponentIds(void);
diff --git a/include/constants/battle_frontier.h b/include/constants/battle_frontier.h
index b5ad4f072..61d9ccb08 100644
--- a/include/constants/battle_frontier.h
+++ b/include/constants/battle_frontier.h
@@ -37,6 +37,7 @@
 #define SPECIAL_BATTLE_STEVEN 8
 #define SPECIAL_BATTLE_PIKE_DOUBLE 9
 #define SPECIAL_BATTLE_PYRAMID 10
+#define SPECIAL_BATTLE_MULTI 11
 
 // For 'ShowFacilityResultsWindow' function which is a part of the 'CallFrontierUtilFunc' special.
 #define RESULTS_LINK_CONTEST 7
diff --git a/include/constants/trainers.h b/include/constants/trainers.h
index 2ea9f7c62..9b333b531 100644
--- a/include/constants/trainers.h
+++ b/include/constants/trainers.h
@@ -13,6 +13,7 @@
 #define TRAINER_LINK_OPPONENT               2048
 #define TRAINER_OPPONENT_C00                3072
 #define TRAINER_STEVEN_PARTNER              3075
+#define TRAINER_CUSTOM_PARTNER              3076
 
 #define TRAINER_PIC_HIKER                  0
 #define TRAINER_PIC_AQUA_GRUNT_M           1
diff --git a/src/battle_bg.c b/src/battle_bg.c
index 51138040c..7bc042bfd 100644
--- a/src/battle_bg.c
+++ b/src/battle_bg.c
@@ -1107,7 +1107,7 @@ void DrawBattleEntryBackground(void)
     }
     else if (gBattleTypeFlags & (BATTLE_TYPE_FRONTIER | BATTLE_TYPE_LINK | BATTLE_TYPE_x2000000 | BATTLE_TYPE_EREADER_TRAINER))
     {
-        if (!(gBattleTypeFlags & BATTLE_TYPE_INGAME_PARTNER) || gPartnerTrainerId == TRAINER_STEVEN_PARTNER)
+        if (!(gBattleTypeFlags & BATTLE_TYPE_INGAME_PARTNER) || gPartnerTrainerId == TRAINER_STEVEN_PARTNER || gPartnerTrainerId >= TRAINER_CUSTOM_PARTNER)
         {
             LZDecompressVram(gBattleTerrainAnimTiles_Building, (void*)(VRAM + 0x4000));
             LZDecompressVram(gBattleTerrainAnimTilemap_Building, (void*)(VRAM + 0xE000));
diff --git a/src/battle_controller_player.c b/src/battle_controller_player.c
index 5da609b15..9f7acdbf0 100644
--- a/src/battle_controller_player.c
+++ b/src/battle_controller_player.c
@@ -2318,7 +2318,7 @@ static void PlayerHandleDrawTrainerPic(void)
         else // First mon, on the left.
             xPos = 32;
 
-        if (gBattleTypeFlags & BATTLE_TYPE_INGAME_PARTNER && gPartnerTrainerId != TRAINER_STEVEN_PARTNER)
+        if (gBattleTypeFlags & BATTLE_TYPE_INGAME_PARTNER && gPartnerTrainerId != TRAINER_STEVEN_PARTNER && gPartnerTrainerId < TRAINER_CUSTOM_PARTNER)
         {
             xPos = 90;
             yPos = (8 - gTrainerFrontPicCoords[trainerPicId].coords) * 4 + 80;
@@ -2336,7 +2336,7 @@ static void PlayerHandleDrawTrainerPic(void)
     }
 
     // Use front pic table for any tag battles unless your partner is Steven.
-    if (gBattleTypeFlags & BATTLE_TYPE_INGAME_PARTNER && gPartnerTrainerId != TRAINER_STEVEN_PARTNER)
+    if (gBattleTypeFlags & BATTLE_TYPE_INGAME_PARTNER && gPartnerTrainerId != TRAINER_STEVEN_PARTNER && gPartnerTrainerId < TRAINER_CUSTOM_PARTNER)
     {
         trainerPicId = PlayerGenderToFrontTrainerPicId(gSaveBlock2Ptr->playerGender);
         DecompressTrainerFrontPic(trainerPicId, gActiveBattler);
diff --git a/src/battle_controller_player_partner.c b/src/battle_controller_player_partner.c
index 65e6c2dd8..3ab8869aa 100644
--- a/src/battle_controller_player_partner.c
+++ b/src/battle_controller_player_partner.c
@@ -1315,6 +1315,12 @@ static void PlayerPartnerHandleDrawTrainerPic(void)
         xPos = 90;
         yPos = (8 - gTrainerBackPicCoords[trainerPicId].coords) * 4 + 80;
     }
+    else if (gPartnerTrainerId >= TRAINER_CUSTOM_PARTNER)
+    {
+        trainerPicId = gPartnerSpriteId;
+        xPos = 90;
+        yPos = (8 - gTrainerBackPicCoords[trainerPicId].coords) * 4 + 80;
+    }
     else
     {
         trainerPicId = GetFrontierTrainerFrontSpriteId(gPartnerTrainerId);
@@ -1323,7 +1329,7 @@ static void PlayerPartnerHandleDrawTrainerPic(void)
     }
 
     // Use back pic only if the partner is Steven
-    if (gPartnerTrainerId == TRAINER_STEVEN_PARTNER)
+    if (gPartnerTrainerId == TRAINER_STEVEN_PARTNER || gPartnerTrainerId >= TRAINER_CUSTOM_PARTNER)
     {
         DecompressTrainerBackPic(trainerPicId, gActiveBattler);
         SetMultiuseSpriteTemplateToTrainerBack(trainerPicId, GetBattlerPosition(gActiveBattler));
@@ -1799,6 +1805,11 @@ static void PlayerPartnerHandleIntroTrainerBallThrow(void)
         u8 spriteId = TRAINER_BACK_PIC_STEVEN;
         LoadCompressedPalette(gTrainerBackPicPaletteTable[spriteId].data, 0x100 + paletteNum * 16, 32);
     }
+    else if (gPartnerTrainerId >= TRAINER_CUSTOM_PARTNER)
+    {
+        u8 spriteId = gPartnerSpriteId;
+        LoadCompressedPalette(gTrainerBackPicPaletteTable[spriteId].data, 0x100 + paletteNum * 16, 32);
+    }
     else
     {
         u8 spriteId = GetFrontierTrainerFrontSpriteId(gPartnerTrainerId);
diff --git a/src/battle_main.c b/src/battle_main.c
index e2101a9c4..6d4a960ff 100644
--- a/src/battle_main.c
+++ b/src/battle_main.c
@@ -191,7 +191,6 @@ EWRAM_DATA u8 gDisplayedStringBattle[300] = {0};
 EWRAM_DATA u8 gBattleTextBuff1[TEXT_BUFF_ARRAY_COUNT] = {0};
 EWRAM_DATA u8 gBattleTextBuff2[TEXT_BUFF_ARRAY_COUNT] = {0};
 EWRAM_DATA u8 gBattleTextBuff3[TEXT_BUFF_ARRAY_COUNT] = {0};
-EWRAM_DATA static u32 sUnusedUnknownArray[25] = {0};
 EWRAM_DATA u32 gBattleTypeFlags = 0;
 EWRAM_DATA u8 gBattleTerrain = 0;
 EWRAM_DATA u32 gUnknown_02022FF4 = 0;
@@ -288,6 +287,7 @@ EWRAM_DATA u8 gBattleMonForms[MAX_BATTLERS_COUNT] = {0};
 EWRAM_DATA u32 gFieldStatuses = 0;
 EWRAM_DATA struct FieldTimer gFieldTimers = {0};
 EWRAM_DATA u8 gBattlerAbility = 0;
+EWRAM_DATA u16 gPartnerSpriteId = 0;
 
 // IWRAM common vars
 void (*gPreBattleCallback1)(void);
@@ -616,7 +616,7 @@ static void CB2_InitBattleInternal(void)
 
     gBattle_WIN0H = 240;
 
-    if (gBattleTypeFlags & BATTLE_TYPE_INGAME_PARTNER && gPartnerTrainerId != TRAINER_STEVEN_PARTNER)
+    if (gBattleTypeFlags & BATTLE_TYPE_INGAME_PARTNER && gPartnerTrainerId != TRAINER_STEVEN_PARTNER && gPartnerTrainerId < TRAINER_CUSTOM_PARTNER)
     {
         gBattle_WIN0V = 159;
         gBattle_WIN1H = 240;
@@ -2693,7 +2693,7 @@ static void sub_80398D0(struct Sprite *sprite)
         {
             sprite->invisible = FALSE;
             sprite->callback = SpriteCallbackDummy_2;
-            sUnusedUnknownArray[0] = 0;
+            // sUnusedUnknownArray[0] = 0;
         }
     }
 }
diff --git a/src/battle_message.c b/src/battle_message.c
index e5ba3d30b..ee47ad46f 100644
--- a/src/battle_message.c
+++ b/src/battle_message.c
@@ -2684,7 +2684,7 @@ static const u8 *BattleStringGetPlayerName(u8 *text, u8 battlerId)
             toCpy = gSaveBlock2Ptr->playerName;
         break;
     case B_POSITION_PLAYER_RIGHT:
-        if (gBattleTypeFlags & (BATTLE_TYPE_RECORDED | BATTLE_TYPE_MULTI))
+        if (gBattleTypeFlags & BATTLE_TYPE_LINK && gBattleTypeFlags & (BATTLE_TYPE_RECORDED | BATTLE_TYPE_MULTI))
         {
             toCpy = gLinkPlayers[2].name;
         }
diff --git a/src/battle_script_commands.c b/src/battle_script_commands.c
index d4175643f..7d856dae6 100644
--- a/src/battle_script_commands.c
+++ b/src/battle_script_commands.c
@@ -3360,7 +3360,7 @@ static bool32 IsBattleLostForPlayer(void)
     u32 i;
     u32 HP_count = 0;
 
-    if (gBattleTypeFlags & BATTLE_TYPE_INGAME_PARTNER && gPartnerTrainerId == TRAINER_STEVEN_PARTNER)
+    if (gBattleTypeFlags & BATTLE_TYPE_INGAME_PARTNER && (gPartnerTrainerId == TRAINER_STEVEN_PARTNER || gPartnerTrainerId >= TRAINER_CUSTOM_PARTNER))
     {
         for (i = 0; i < 3; i++)
         {
diff --git a/src/battle_setup.c b/src/battle_setup.c
index 3913cabb1..d42f57237 100644
--- a/src/battle_setup.c
+++ b/src/battle_setup.c
@@ -79,7 +79,6 @@ static void DoStandardWildBattle(bool32 isDouble);
 static void CB2_EndWildBattle(void);
 static void CB2_EndScriptedWildBattle(void);
 static u8 GetWildBattleTransition(void);
-static u8 GetTrainerBattleTransition(void);
 static void sub_80B1218(void);
 static void sub_80B1234(void);
 static void CB2_GiveStarter(void);
@@ -795,7 +794,7 @@ static u8 GetWildBattleTransition(void)
     }
 }
 
-static u8 GetTrainerBattleTransition(void)
+u8 GetTrainerBattleTransition(void)
 {
     u8 minPartyCount;
     u8 transitionType;
diff --git a/src/battle_tower.c b/src/battle_tower.c
index 165b6bf64..b4a92a846 100644
--- a/src/battle_tower.c
+++ b/src/battle_tower.c
@@ -792,6 +792,10 @@ u8 GetFrontierOpponentClass(u16 trainerId)
     {
         trainerClass = gTrainers[TRAINER_STEVEN].trainerClass;
     }
+    else if (trainerId >= TRAINER_CUSTOM_PARTNER)
+    {
+        trainerClass = gTrainers[trainerId - TRAINER_CUSTOM_PARTNER].trainerClass;
+    }
     else if (trainerId < TRAINER_RECORD_MIXING_FRIEND)
     {
         trainerClass = gFacilityClassToTrainerClass[gFacilityTrainers[trainerId].facilityClass];
@@ -875,6 +879,11 @@ void GetFrontierTrainerName(u8 *dst, u16 trainerId)
         for (i = 0; i < PLAYER_NAME_LENGTH; i++)
             dst[i] = gTrainers[TRAINER_STEVEN].trainerName[i];
     }
+    else if (trainerId >= TRAINER_CUSTOM_PARTNER)
+    {
+        for (i = 0; gTrainers[trainerId - TRAINER_CUSTOM_PARTNER].trainerName[i] != EOS; i++)
+            dst[i] = gTrainers[trainerId - TRAINER_CUSTOM_PARTNER].trainerName[i];
+    }
     else if (trainerId < TRAINER_RECORD_MIXING_FRIEND)
     {
         for (i = 0; i < PLAYER_NAME_LENGTH; i++)
@@ -1463,6 +1472,19 @@ void DoSpecialTrainerBattle(void)
         PlayMapChosenOrBattleBGM(0);
         BattleTransition_StartOnField(B_TRANSITION_MAGMA);
         break;
+    case SPECIAL_BATTLE_MULTI:
+        gBattleTypeFlags = BATTLE_TYPE_TRAINER | BATTLE_TYPE_DOUBLE | BATTLE_TYPE_TWO_OPPONENTS | BATTLE_TYPE_MULTI | BATTLE_TYPE_INGAME_PARTNER;
+        gPartnerSpriteId = gSpecialVar_0x8007;
+        FillPartnerParty(gSpecialVar_0x8006 + TRAINER_CUSTOM_PARTNER);
+        gApproachingTrainerId = 0;
+        BattleSetup_ConfigureTrainerBattle(MossdeepCity_SpaceCenter_2F_EventScript_224157 + 1);
+        gApproachingTrainerId = 1;
+        BattleSetup_ConfigureTrainerBattle(MossdeepCity_SpaceCenter_2F_EventScript_224166 + 1);
+        gPartnerTrainerId = gSpecialVar_0x8006 + TRAINER_CUSTOM_PARTNER;
+        CreateTask(Task_StartBattleAfterTransition, 1);
+        PlayMapChosenOrBattleBGM(0);
+        BattleTransition_StartOnField(GetTrainerBattleTransition());
+        break;
     }
 }
 
@@ -2307,6 +2329,14 @@ static void FillPartnerParty(u16 trainerId)
             CalculateMonStats(&gPlayerParty[3 + i]);
         }
     }
+    else if (trainerId >= TRAINER_CUSTOM_PARTNER)
+    {
+        for (i = 0; i < 3; i++)
+        {
+            // Temporary.
+            CreateMon(&gPlayerParty[3 + i], Random() % NUM_SPECIES, Random() % MAX_LEVEL, Random() % 31, 0, 0, 0, 0);
+        }
+    }
     else if (trainerId == TRAINER_EREADER)
     {
         // Scrapped, lol.