diff --git a/asm/enterPortalSubtask.s b/asm/enterPortalSubtask.s
deleted file mode 100644
index e1778d69..00000000
--- a/asm/enterPortalSubtask.s
+++ /dev/null
@@ -1,298 +0,0 @@
-	.include "asm/macros.inc"
-	.include "constants/constants.inc"
-
-	.syntax unified
-
-	.text
-
-	thumb_func_start sub_0804AB70
-sub_0804AB70: @ 0x0804AB70
-	push {r4, r5, lr}
-	movs r0, #0
-	bl DispReset
-	ldr r1, _0804ABF8 @ =gScreen
-	movs r2, #0
-	movs r0, #0x92
-	lsls r0, r0, #5
-	strh r0, [r1]
-	ldr r0, _0804ABFC @ =0x00009E83
-	strh r0, [r1, #0x14]
-	ldr r0, _0804AC00 @ =gRoomControls
-	strh r2, [r1, #0x16]
-	strh r2, [r0, #0xa]
-	strh r2, [r1, #0x18]
-	strh r2, [r0, #0xc]
-	ldr r0, _0804AC04 @ =gArea
-	ldrb r5, [r0, #0x17]
-	cmp r5, #2
-	bne _0804ABA4
-	ldr r0, _0804AC08 @ =gUI
-	adds r0, #0x20
-	ldrb r0, [r0]
-	cmp r0, #2
-	beq _0804ABA4
-	movs r5, #3
-_0804ABA4:
-	lsls r4, r5, #1
-	ldr r0, _0804AC0C @ =gUnk_080D4138
-	adds r4, r4, r0
-	ldrb r0, [r4]
-	bl LoadPaletteGroup
-	ldrb r0, [r4, #1]
-	bl LoadGfxGroup
-	ldr r0, _0804AC10 @ =gUnk_02017700
-	movs r2, #0x90
-	lsls r2, r2, #2
-	adds r1, r0, r2
-	movs r2, #0x20
-	bl MemCopy
-	ldr r2, _0804AC14 @ =gUsedPalettes
-	ldr r0, [r2]
-	movs r1, #0x80
-	lsls r1, r1, #0xe
-	orrs r0, r1
-	str r0, [r2]
-	bl EraseAllEntities
-	ldr r1, _0804AC18 @ =gUnk_080D4110
-	lsls r0, r5, #2
-	adds r0, r0, r1
-	ldr r0, [r0]
-	bl LoadRoomEntityList
-	bl ResetSystemPriority
-	ldr r1, _0804AC04 @ =gArea
-	ldrb r0, [r1, #0xe]
-	adds r0, #1
-	strb r0, [r1, #0xe]
-	movs r0, #4
-	movs r1, #8
-	bl SetFade
-	pop {r4, r5, pc}
-	.align 2, 0
-_0804ABF8: .4byte gScreen
-_0804ABFC: .4byte 0x00009E83
-_0804AC00: .4byte gRoomControls
-_0804AC04: .4byte gArea
-_0804AC08: .4byte gUI
-_0804AC0C: .4byte gUnk_080D4138
-_0804AC10: .4byte gUnk_02017700
-_0804AC14: .4byte gUsedPalettes
-_0804AC18: .4byte gUnk_080D4110
-
-	thumb_func_start sub_0804AC1C
-sub_0804AC1C: @ 0x0804AC1C
-	push {r4, lr}
-	bl UpdateEntities
-	ldr r0, _0804AC98 @ =gUnk_02018EB0
-	ldr r2, [r0, #0x14]
-	cmp r2, #0
-	beq _0804AC5E
-	ldr r3, _0804AC9C @ =gRoomControls
-	movs r1, #0xc
-	ldrsh r0, [r3, r1]
-	movs r4, #0x32
-	ldrsh r1, [r2, r4]
-	subs r1, #0x50
-	subs r0, r0, r1
-	movs r4, #0x36
-	ldrsh r1, [r2, r4]
-	subs r1, r0, r1
-	cmp r1, #0
-	beq _0804AC5E
-	ldrh r0, [r3, #0xc]
-	subs r0, r0, r1
-	strh r0, [r3, #0xc]
-	lsls r0, r0, #0x10
-	cmp r0, #0
-	bge _0804AC52
-	movs r0, #0
-	strh r0, [r3, #0xc]
-_0804AC52:
-	movs r1, #0xc
-	ldrsh r0, [r3, r1]
-	cmp r0, #0x9f
-	ble _0804AC5E
-	movs r0, #0x9f
-	strh r0, [r3, #0xc]
-_0804AC5E:
-	ldr r2, _0804ACA0 @ =gScreen
-	ldr r1, _0804AC9C @ =gRoomControls
-	ldrh r0, [r1, #0xa]
-	strh r0, [r2, #0x16]
-	ldrh r0, [r1, #0xc]
-	strh r0, [r2, #0x18]
-	bl FlushSprites
-	bl DrawEntities
-	bl CopyOAM
-	ldr r0, _0804AC98 @ =gUnk_02018EB0
-	ldrb r0, [r0, #0x1b]
-	cmp r0, #0
-	bne _0804AC86
-	bl sub_0804ACA8
-	cmp r0, #0
-	beq _0804AC96
-_0804AC86:
-	ldr r1, _0804ACA4 @ =gArea
-	ldrb r0, [r1, #0xe]
-	adds r0, #1
-	strb r0, [r1, #0xe]
-	movs r0, #7
-	movs r1, #0x10
-	bl SetFade
-_0804AC96:
-	pop {r4, pc}
-	.align 2, 0
-_0804AC98: .4byte gUnk_02018EB0
-_0804AC9C: .4byte gRoomControls
-_0804ACA0: .4byte gScreen
-_0804ACA4: .4byte gArea
-
-	thumb_func_start sub_0804ACA8
-sub_0804ACA8: @ 0x0804ACA8
-	push {lr}
-	ldr r0, _0804ACC0 @ =gInput
-	ldrh r1, [r0, #2]
-	movs r0, #0x81
-	lsls r0, r0, #1
-	ands r0, r1
-	cmp r0, #0
-	beq _0804ACC4
-	bl sub_0804AD18
-	b _0804ACC6
-	.align 2, 0
-_0804ACC0: .4byte gInput
-_0804ACC4:
-	movs r0, #0
-_0804ACC6:
-	pop {pc}
-
-	thumb_func_start sub_0804ACC8
-sub_0804ACC8: @ 0x0804ACC8
-	push {lr}
-	ldr r0, _0804ACEC @ =gFadeControl
-	ldrb r0, [r0]
-	cmp r0, #0
-	bne _0804ACE8
-	ldr r0, _0804ACF0 @ =gArea
-	ldrb r0, [r0, #0x17]
-	adds r0, #0x5e
-	bl SetGlobalFlag
-	ldr r0, _0804ACF4 @ =gUnk_02032EDC
-	bl sub_0804AD6C
-	movs r0, #0
-	bl sub_080A71F4
-_0804ACE8:
-	pop {pc}
-	.align 2, 0
-_0804ACEC: .4byte gFadeControl
-_0804ACF0: .4byte gArea
-_0804ACF4: .4byte gUnk_02032EDC
-
-	thumb_func_start RespawnAsMinish
-RespawnAsMinish: @ 0x0804ACF8
-	push {lr}
-	bl sub_0804AD18
-	cmp r0, #0
-	beq _0804AD12
-	ldr r0, _0804AD14 @ =gRoomControls
-	bl sub_0804AD6C
-	bl SetInitializationPriority
-	movs r0, #0xf8
-	bl SoundReq
-_0804AD12:
-	pop {pc}
-	.align 2, 0
-_0804AD14: .4byte gRoomControls
-
-	thumb_func_start sub_0804AD18
-sub_0804AD18: @ 0x0804AD18
-	push {lr}
-	ldr r0, _0804AD30 @ =gArea
-	ldrb r1, [r0, #0x17]
-	adds r2, r0, #0
-	cmp r1, #6
-	bhi _0804AD66
-	lsls r0, r1, #2
-	ldr r1, _0804AD34 @ =_0804AD38
-	adds r0, r0, r1
-	ldr r0, [r0]
-	mov pc, r0
-	.align 2, 0
-_0804AD30: .4byte gArea
-_0804AD34: .4byte _0804AD38
-_0804AD38: @ jump table
-	.4byte _0804AD54 @ case 0
-	.4byte _0804AD54 @ case 1
-	.4byte _0804AD54 @ case 2
-	.4byte _0804AD66 @ case 3
-	.4byte _0804AD66 @ case 4
-	.4byte _0804AD66 @ case 5
-	.4byte _0804AD62 @ case 6
-_0804AD54:
-	ldrb r0, [r2, #0x17]
-	adds r0, #0x5e
-	bl CheckGlobalFlag
-	adds r1, r0, #0
-	cmp r1, #0
-	bne _0804AD68
-_0804AD62:
-	movs r0, #0
-	b _0804AD68
-_0804AD66:
-	movs r0, #0
-_0804AD68:
-	pop {pc}
-	.align 2, 0
-
-	thumb_func_start sub_0804AD6C
-sub_0804AD6C: @ 0x0804AD6C
-	push {r4, r5, r6, lr}
-	mov r6, r8
-	push {r6}
-	ldr r3, _0804ADD0 @ =gRoomTransition
-	movs r1, #0
-	movs r6, #1
-	strb r6, [r3, #8]
-	strb r1, [r3, #9]
-	ldr r4, _0804ADD4 @ =gArea
-	ldr r5, _0804ADD8 @ =gUnk_080D4140
-	ldrb r1, [r4, #0x16]
-	lsls r1, r1, #2
-	adds r1, r1, r5
-	ldrh r1, [r1]
-	ldrh r2, [r4, #0x12]
-	adds r1, r1, r2
-	ldrh r2, [r0, #6]
-	subs r1, r1, r2
-	movs r2, #0
-	mov r8, r2
-	strh r1, [r3, #0x10]
-	ldrb r1, [r4, #0x16]
-	lsls r1, r1, #1
-	adds r1, #1
-	lsls r1, r1, #1
-	adds r1, r1, r5
-	ldrh r1, [r1]
-	ldrh r2, [r4, #0x14]
-	adds r1, r1, r2
-	ldrh r2, [r0, #8]
-	subs r1, r1, r2
-	strh r1, [r3, #0x12]
-	ldrb r1, [r4, #0x16]
-	lsls r1, r1, #1
-	strb r1, [r3, #0xe]
-	strb r6, [r3, #0xf]
-	ldrb r1, [r0, #4]
-	strb r1, [r3, #0xc]
-	ldrb r0, [r0, #5]
-	strb r0, [r3, #0xd]
-	mov r0, r8
-	strb r0, [r3, #0x14]
-	bl ClearArmosData
-	bl sub_080300C4
-	pop {r3}
-	mov r8, r3
-	pop {r4, r5, r6, pc}
-	.align 2, 0
-_0804ADD0: .4byte gRoomTransition
-_0804ADD4: .4byte gArea
-_0804ADD8: .4byte gUnk_080D4140
diff --git a/include/main.h b/include/main.h
index c5e0c0c5..c6be0f37 100644
--- a/include/main.h
+++ b/include/main.h
@@ -2,6 +2,7 @@
 #define MAIN_H
 
 #include "global.h"
+#include "room.h" // just to get the type of screenTransitionData
 
 /** File signature */
 #define SIGNATURE 'MCZ3'
@@ -78,7 +79,9 @@ typedef struct {
     /*0x07*/ u8 pauseFadeIn;
     /*0x08*/ u16 isLoading;
     /*0x0A*/ u16 fadeInTime;
-    /*0x0C*/ u8 fillerC[0x3A8];
+    /*0x0C*/ u8 fillerC[0x10];
+    /*0x1c*/ RoomControls unk_1c;
+    /*0x2e*/ u8 unk_2e[0x364];
 } UI;
 static_assert(sizeof(UI) == 0x3b4);
 
diff --git a/linker.ld b/linker.ld
index a57066cd..a4e265a7 100644
--- a/linker.ld
+++ b/linker.ld
@@ -430,7 +430,6 @@ SECTIONS {
         src/enemyUtils.o(.text);
         src/createEnemy.o(.text);
         src/enterPortalSubtask.o(.text);
-        asm/enterPortalSubtask.o(.text);
         src/room.o(.text);
         src/roomInit.o(.text);
         src/fade.o(.text);
diff --git a/src/enterPortalSubtask.c b/src/enterPortalSubtask.c
index e43094c8..ad35d468 100644
--- a/src/enterPortalSubtask.c
+++ b/src/enterPortalSubtask.c
@@ -7,18 +7,36 @@
 #include "object.h"
 #include "functions.h"
 #include "game.h"
+#include "fileselect.h"
 
 typedef struct {
     u8 filler[18];
-    u32 unk;
+    Entity* unk_14;
+    u8 unk_18;
+    u8 unk_19;
+    u8 unk_1a;
+    u8 unk_1b;
 } struct_02018EB0;
 
+extern void ClearArmosData(void);
+extern void sub_080300C4(void);
+
+extern struct_02018EB0 gUnk_02018EB0;
+extern u16 gUnk_020178E0[];
+extern u8 gUnk_02017700[];
+
 extern void (*const gUnk_080D4120[])(void);
 extern void (*const gUnk_080D412C[])(void);
+extern const u16 gUnk_080D4140[];
+extern const u8 gUnk_080D4138[];
+extern const EntityData* gUnk_080D4110[];
 
-extern struct_02018EB0 gUnk_02018EB0;
+bool32 sub_0804AD18(void);
+void sub_0804AD6C(RoomControls*);
+void sub_080A71F4(ScreenTransitionData*);
+bool32 sub_0804ACA8(void);
 
-u32 IsEnterPortal(void) {
+bool32 IsEnterPortal(void) {
     if (gArea.playShrinkSeq) {
         gMain.substate = GAMEMAIN_MINISHPORTAL;
         gArea.filler[8] = 0;
@@ -39,7 +57,7 @@ void GameMain_MinishPortal(void) {
 
 void sub_0804AAD4(void) {
     MemClear(&gUnk_02018EB0, 0x28);
-    gUnk_02018EB0.unk = 0;
+    gUnk_02018EB0.unk_14 = NULL;
     EraseAllEntities();
     CreateObject(OBJECT_3D, gArea.curPortalType, 0);
     gArea.filler[8]++;
@@ -67,3 +85,120 @@ void sub_0804AB24(void) {
 void Subtask_PortalCutscene(void) {
     gUnk_080D412C[gArea.filler[8]]();
 }
+void sub_0804AB70(void) {
+    const u8* ptr;
+    RoomControls* controls;
+    u32 portalId;
+
+    DispReset(0);
+    gScreen.lcd.displayControl = 0x1240;
+    gScreen.bg1.control = 0x9e83;
+    controls = &gRoomControls;
+    gScreen.bg1.xOffset = 0;
+    controls->scroll_x = 0;
+    gScreen.bg1.yOffset = 0;
+    controls->scroll_y = 0;
+    portalId = gArea.curPortalType;
+    if ((portalId == 2) && (gUI.unk_1c.area != 2)) {
+        portalId = 3;
+    }
+    ptr = &gUnk_080D4138[portalId * 2];
+    LoadPaletteGroup(ptr[0]);
+    LoadGfxGroup(ptr[1]);
+    MemCopy(&gUnk_02017700, gUnk_02017700 + 0x240, 0x20);
+    gUsedPalettes |= 0x200000;
+    EraseAllEntities();
+    LoadRoomEntityList((EntityData*)gUnk_080D4110[portalId]);
+    ResetSystemPriority();
+    gArea.filler3[0]++;
+    SetFade(4, 8);
+}
+
+void sub_0804AC1C(void) {
+    s32 tmp;
+
+    UpdateEntities();
+    if (gUnk_02018EB0.unk_14 != NULL) {
+        tmp = gRoomControls.scroll_y + 0x50 - gUnk_02018EB0.unk_14->y.HALF.HI - gUnk_02018EB0.unk_14->z.HALF.HI;
+        if (tmp != 0) {
+            tmp = gRoomControls.scroll_y = gRoomControls.scroll_y - tmp;
+            if (tmp * 0x10000 < 0) {
+                gRoomControls.scroll_y = 0;
+            }
+            if (0x9f < gRoomControls.scroll_y) {
+                gRoomControls.scroll_y = 0x9f;
+            }
+        }
+    }
+    gScreen.bg1.xOffset = gRoomControls.scroll_x;
+    gScreen.bg1.yOffset = gRoomControls.scroll_y;
+    FlushSprites();
+    DrawEntities();
+    CopyOAM();
+    if ((gUnk_02018EB0.unk_1b != 0) || sub_0804ACA8()) {
+        gArea.filler3[0]++;
+        SetFade(7, 0x10);
+    }
+}
+
+bool32 sub_0804ACA8(void) {
+    if ((gInput.newKeys & (R_BUTTON | B_BUTTON)) == 0) {
+        return 0;
+    } else {
+        return sub_0804AD18();
+    }
+}
+
+void sub_0804ACC8(void) {
+    if (gFadeControl.active == 0) {
+        SetGlobalFlag(gArea.curPortalType + ENTRANCE_0);
+        sub_0804AD6C((RoomControls*)&gUI.unk_1c);
+        sub_080A71F4(0);
+    }
+}
+
+void RespawnAsMinish(void) {
+    if (sub_0804AD18()) {
+        sub_0804AD6C(&gRoomControls);
+        SetInitializationPriority();
+        SoundReq(SFX_F8);
+    }
+}
+
+bool32 sub_0804AD18(void) {
+    switch (gArea.curPortalType) {
+        case 0:
+        case 1:
+        case 2:
+            if (!CheckGlobalFlag(ENTRANCE_0 + gArea.curPortalType)) {
+                return FALSE;
+            }
+            // else: return TRUE implicitely, because it's stored in r0. But does not match if returning explicitely.
+            break;
+        case 6:
+            return FALSE;
+        case 3:
+        case 4:
+        case 5:
+        default:
+            return FALSE;
+    }
+}
+
+void sub_0804AD6C(RoomControls* controls) {
+    Area* area;
+    gRoomTransition.transitioningOut = 1;
+    gRoomTransition.type = 0;
+    area = &gArea;
+    gRoomTransition.player_status.start_pos_x =
+        (area->curPortalX + gUnk_080D4140[area->curPortalExitDirection * 2]) - controls->origin_x;
+    gRoomTransition.player_status.start_pos_y =
+        (area->curPortalY + gUnk_080D4140[area->curPortalExitDirection * 2 + 1]) - controls->origin_y;
+    gRoomTransition.player_status.start_anim = area->curPortalExitDirection << 1;
+    gRoomTransition.player_status.spawn_type = 1;
+    gRoomTransition.player_status.area_next = controls->area;
+    gRoomTransition.player_status.room_next = controls->room;
+    gRoomTransition.player_status.layer = 0;
+    ClearArmosData();
+    sub_080300C4();
+}
diff --git a/src/game.c b/src/game.c
index a233b508..7700c919 100644
--- a/src/game.c
+++ b/src/game.c
@@ -98,7 +98,7 @@ extern void DeleteSleepingEntities(void);
 extern u32 UpdateLightLevel(void);
 extern void sub_080185F8(void);
 extern void UpdateDoorTransition(void);
-extern u32 IsEnterPortal(void);
+extern bool32 IsEnterPortal(void);
 extern void UpdateCarriedObject(void);
 extern void DrawUI(void);
 extern u32 CheckPlayerInactive(void);