Pacifist - True Laboratory

This page tells you how to get through the True Laboratory section in Undertale which is only accessible on a true Pacifist run after completing New Home.

It seems you've escaped and Sans will give you a rundown of what's happened over the phone, and you'll get to talk to some of your other friends too.

Flowey will show up again and tell you to reload your save and go visit Dr Alphys for a better ending.

This will put you back to before you fought Asgore but the game will remember. Head south back towards Dr Alphys' Lab to keep playing. On your way, Undyne will call asking you to come by to do her a favour. She's at Papyrus' house in Snowdin, so forget about the Lab for now and go there first.

Undyne has a letter for you to take to Dr Alphys. You'll be threatened with death if you read it but you can't open it anyway so there's little risk of that. Jump back on the ferry and go back to the Hotland with Dr Alphys' Lab.

All you can do is slide the letter under the door. Unfortunately, Undyne didn't sign it so Alphys will think this declaration of love is from you and the two of you will go on a date.

As with any date scene, you can choose any option you want while you watch the fun.

Undyne will show up and send Dr Alphys off with Papyrus to learn some confidence and you'll find yourself alone in the sewer where you fought that practice dummy so long ago.

Head through the linear path in the sewer and you'll come out back in Waterfall. To get back to the lab go right past the save point and south at the turtle shop. Take the boat back to the Hotlands and go right.

Once inside keep heading to the right until you come to a room with a note in front of it. Read it and head into the room.

Take the elevator down to the basement. There's a lot of story down here, so get ready to read all the terminals as you head right, down the corridor and then north.

This room has a save point, so do so as you will encounter enemies here. You can see a door with four colours on it - these are the colours of the keys you will need to find.

Keep reading all the notes and terminals you find and go left.

At the end of this room you'll find a set of 3 sinks, turn them all on and you'll start an encounter.

Memory Head

You'll need to 'Cell' each one to spare them. Dodge their attacks by moving quickly away from the white circles that appear. Ared key will appear in the sink when you're done - take the door next to the sinks and put the key in the box at the end.

Now go back to the save room and up through the nothern right-hand door. Keep heading right til you come to a room with some beds. The left-most bed in the center has the sheets pulled up. Check it to get the yellow key, take it and head through the northern door.

Start by heading right and you'll find a room with many fans and some smoke. At the far end of the room is a button, push it to clear the smoke. This will also trigger another encounter.

Amalgamate

Amalgamate is very similar to a previous battle. Choose, beckon, pet, play, pet, pet, to spare him.

Now head out of the room and head left til you come to a doorway north. Go through it and head straight up to the spooky curtain to get the green key.

Go left and you'll come to another room with a large skull and a save point.

Go through the door on the right of the skull to use the yellow key. You can also watch some videos which give more insight into the story on the tv here. Now Interact with the save point to find it's really another encounter.

Lemon Bread

You need to hum, flex, and unhug lemon bread to spare him, now keep heading on past to the left.

This room has some refrigerators and despite the suspicious nature of the one that is jumping around, it's the last one where you'll get another encounter.

Amalgamate 2

This time you'll need to 'joke' multiple times until you can spare her, then you can grab the blue key and head through the door to use the green one.

Backtrack to the room with the beds and save, just in case. Now go through the eastern corridor. As you pass the mirrors you'll have another encounter.

Reaper Bird

Pick on, Mystify, and Pray and Reaper Bird can be spared, then continue through the door to use the blue key.

Now you can make your way back to the room with the door with several locks and go through it. You'll find a room at the end with the elevator power control, use it to turn the power back on.

You'll suddenly see multiple monsters heading towards you. Alphys will come in and stop them, saying they're just hungry. She'll also explain much of what you probably learned through reading the terminals and say she wants to come clean.

When you go back into the elevator you'll recieve a phone call and be transported back to the New Home area. You can't go back through the lift, so head along the corridor and back to the throne room to face Asgore again.

Before the two of you can fight, Toriel will knock him out of the way. Undyne, Dr Alphys, Papyrus, and Sans will all also show up to try to stop the fight. It looks like a happy ending until once again, Flowey shows up and captures everyone.

Asriel

Flowey will reveal himself to be Asriel, and the proper final boss fight will begin.

This fight isn't too bad as your actions make it a lot easier. Choose 'Hope' to reduce the damage done in the next turn, and Dream to fill your inventory with healing items. Alternate these and using the items as needed to survive - it's a good idea to heal whenever you're below 10 health as he can easily wipe that much off you.

Asriel's Attacks:

• Star Blazing - Stars will come at the box. Stay in the lower left-hand corner. The last large star will explode and send out smaller stars so be careful.
• Shocker Breaker - exclamation boxes will appear just before the lightning, try to keep moving to avoid them.
• Chaos Saber - be on the side of the box Asriel has moved to to avoid the attacks, then for the final move stay in the middle.
• Chaos Buster - Be wherever the lasers aren't to avoid the shots - the final move will send out a large beam so be as far away from where it's pointing as possible.
• Black Hole - he'll fill up the whole screen and start sucking in diamonds. Stay as far away from the centre as possible to not get sucked in.

Now Asriel will say he's only been using a small portion of his power and will transform into a winged beast.

All you can do for a few turns is 'struggle' and dodge his incoming attacks. If you die your heart will refuse to give up and put itself back together.

Your act button will soon transform into a 'Save' button and you can choose to save each of your friends. Each friend will attack you similar to their respective boss fights and you'll need to choose the right actions to remind them of your friendship.

• Undyne - Fake Hit, Recipe, Clash.
• Papyrus - Puzzle, Recipe. 
• Sans - Take Break.
• Alphys - Encourage, Nerd out, Call.
• Toriel - Preference, Hug
• Asgore - Mercy, Talk.

Choose to save once more when your friends are all saved and you'll be able to save Asriel himself. Keep doing so and dodging his attacks which will get less and less intense.

The battle will end and you'll talk to Asriel and you can choose to forgive and console him as he lets all the other souls free and opens the barrier.

You will wake up surrounded by the friends you've made and they'll talk about going through the barrier. 

You can head straight through to the right for the final cutscene but talking to each of them first is worth it for fun dialogue. You can also head back through the world and talk to other characters you've met along the way. The ruins are open again as well and they're worth going back to where you can find a secret in the first area where you originally fell down and began your journey.