Undertale: 10 Pro Tips to Achieve the Pacifist Ending and Spare Every Monster

Introduction

Undertale is a game that famously encourages players to solve conflicts without killing. Achieving the true pacifist ending requires not only sparing every monster but also performing specific actions and secrets. Whether you're a first-time player or aiming for that golden ending, these 10 pro tips will guide you through the Underground with kindness and intrigue.

1. Always Choose 'Act' Over 'Fight'

The golden rule of pacifism in Undertale: never select 'Fight' unless the game forces you (and even then, find an alternative). Use the 'Act' menu to interact with monsters in non-violent ways. Each monster has a unique set of actions—complimenting, joking, or flirting—that can raise their mercy meter. Once the monster's name turns yellow, you can spare them.

2. Listen to Toriel's Lessons

During the Ruins, Toriel teaches you the basics of mercy. Pay close attention: she demonstrates how to spare enemies by showing mercy after a few acts. Follow her example with every monster. Also, when facing Toriel herself, do not attack. Keep sparing her until she stops fighting—this is critical for the pacifist route.

3. Spare Every Boss, No Exceptions

For the true pacifist ending, you must spare all major bosses, including Toriel, Papyrus, Undyne, Mettaton, and Asgore. Each has a specific method: for Papyrus, you need to initiate a date; for Undyne, you must befriend her after the fight; for Mettaton, entertain him enough to lower his ratings. Never kill any boss, or you'll lock yourself out of the best ending.

4. Befriend Undyne After Her Chase

After the Undyne chase sequence in Waterfall, return to Hotland and hang out with her at her house. This is not optional. You must give her water during the chase and then later visit her home. The date with Undyne is essential for unlocking the true pacifist path. Without it, you cannot proceed.

5. Complete Papyrus's Hangout

Papyrus is easy to spare, but you also need to accept his invitation to hang out. After sparing him in Snowdin, go to his house and engage in the 'date.' It’s a quirky, memorable event that also awards you the 'Papyrus' phone call, which later helps befriend Undyne.

6. Explore Every Area Thoroughly

The pacifist route requires interacting with NPCs and finding hidden items. Talk to everyone multiple times, especially after major events. Pay attention to the sign in Snowdin about the 'mysterious key'—it leads to a secret lab in Hotland. Also, collect all the pieces of the 'artifact' in Waterfall to earn a special call.

7. Don't Kill Any Random Encounters

It's tempting to flee from random encounters, but fleeing is fine—it doesn't count as murder. However, if you accidentally kill enemies, you'll deviate from the pacifist path. If you kill even one monster, you're locked out of the true pacifist ending. Use the 'Spare' command only after you've successfully 'Acted' to turn them yellow.

8. Return to the Ruins After Beating Asgore

After defeating Asgore (but not killing him), do not reset. Instead, backtrack to the Ruins and visit Toriel's home. There, you'll trigger a phone call from Sans that leads to the 'Alphys' date. This is the final step before the true lab. If you miss this, you'll only get the neutral ending.

9. Navigate the True Lab's Puzzles

The True Lab in Hotland's hidden area contains disturbing amalgamates. To complete the pacifist run, you must explore all rooms, read the diaries, and face the final boss (Asriel Dreemurr). The puzzles are straightforward—move items to platforms and fill cups with water—but the emotional impact is huge. Persevere.

10. Save and Reset with Caution

If you accidentally kill a monster, you can reload a prior save. However, Undertale remembers your actions across resets (for certain characters). For a clean pacifist run, don't reset after killing unless you're willing to start a new file. The game's consequences are permanent within a save file, so be mindful.

Conclusion

Undertale's pacifist ending is one of gaming's most rewarding experiences. By following these tips, you'll spare every monster, befriend every boss, and unlock the true lab. The journey is filled with humor, heart, and a few tears. Stay determined, and enjoy the best ending the Underground has to offer.