Undertale’s Ultimate Challenge: A Comprehensive Guide to Beating Sans

Sans, the seemingly laid-back skeleton, is arguably the most infamous and challenging boss in Toby Fox’s indie masterpiece, Undertale. His battle isn’t just about brute force; it’s a test of your understanding of the game’s mechanics, your patience, and your ability to learn from your mistakes. This guide will break down his attacks, provide strategies, and offer tips to help you finally overcome this formidable foe and claim victory.

Understanding the Genocide Route and Why Sans is So Difficult

Sans only appears as a boss in the Genocide Route, a path in Undertale where you systematically kill every monster you encounter. This route leads to a drastically different ending and story, and it’s designed to be emotionally jarring. Sans isn’t just a challenging fight; he’s a reflection of your actions, a karmic consequence of your genocidal rampage. He knows about your power to reset timelines, and his fight is a desperate attempt to stop you from continuing your path of destruction.

His difficulty stems from several factors:

• Karma: Sans inflicts “karmic retribution,” often referred to as KR, alongside his regular damage. This effect bypasses your invincibility frames and deals consistent damage over time, forcing you to stay vigilant.
• Low Defense: Sans has a defense of 1, making the battle essentially a marathon of dodging rather than a slugfest. You won’t win by simply tanking hits; you have to learn to avoid them.
• Unconventional Attacks: His attacks are unpredictable, using bones, Gaster Blasters, and platforming elements, demanding quick reflexes and an understanding of his patterns.
• Multiple Attack Phases: The battle is broken down into several phases, each with its own unique set of attacks and challenges.
• The Final Stand: The fight is designed to feel unfair, which it kind of is. It is supposed to be extremely difficult.

Preparing for the Battle: Gear, Items, and Mindset

Before even thinking about facing Sans, you need to be properly prepared. This isn’t just about having the best gear; it’s about having the right mindset and strategy.

Recommended Equipment:

• Weapon: The Burnt Pan. This item heals an extra 4 hp each time you heal. Since the fight with Sans is designed to be a battle of attrition, more healing is vital. Alternatively, the Torn Notebook if your main goal is just to deal as much damage as possible in a short period.
• Armor: The Cloudy Glasses. This armor has the lowest defense in the game, but it is vital for the purpose of this fight. It boosts your invincibility frames which will be important to properly time your movements to dodge Sans’ attack. Alternatively, the Temmie Armor is also a great choice if you would like to have a higher defense while still being able to boost your invincibility frames.

Essential Healing Items:

You’ll need as much healing as possible for this grueling battle. Here’s a list of must-have items:

• Instant Noodles: Heal for 90HP (a great source of healing)
• Legendary Hero: Heal for 40HP (a great choice for a quick heal)
• Face Steak: Heal for 60HP (a great choice if you don’t have the other items)
• Snowman Piece: Heal for 45HP (a good backup item)
• Sea Tea: Heal for 10 HP with an increase of 1 speed which lasts for the entire fight (a must have to move through attacks faster)

Note: You cannot go back to shops once you’ve started the battle, so make sure you are fully stocked before engaging Sans.

Mindset and Strategy:

• Patience is Key: You will die, a lot. Don’t get discouraged. Focus on learning his patterns and adjusting your strategies accordingly.
• Consistent Practice: Repetition is crucial. It will not be easy at first but you will find success with enough time and effort.
• Use Your Invincibility Frames Wisely: When you take damage, you are invulnerable for a short period. Utilize these invincibility frames by strategically moving through bones and attacks.
• Focus on Defense, Not Offense: Sans’s battle is not a sprint; it’s a marathon. Try to stay alive as long as possible and avoid getting hit.
• Learn From Each Failure: Each time you fail, analyze what went wrong, and adjust your strategy accordingly.

Detailed Breakdown of Sans’ Attacks

Sans’ attacks are a combination of bones, Gaster Blasters, and strategic movement, and understanding each of these is crucial to success.

Phase 1: The Beginning Barrage

Phase 1 is a fast-paced sequence of attacks designed to throw you off guard and establish his dominance. Here is a breakdown of what to expect:

• Bone Tosses:
  • Description: Sans will throw bones from various directions, at different speeds. Some will be static while others will move across the box.
  • Strategy: Pay close attention to their trajectory, and try to keep yourself centered in the middle of the box. This will make it easier to dodge them regardless of their position. Use your invincibility frames to move through bones when needed.
• Blue Attacks:
  • Description: Blue bones require you to stay still or you will take damage, this adds to the challenge since most of the time you will have to quickly move to avoid the white bones.
  • Strategy: Once you see the blue bones, plan your movement around it. If they are slow moving you may be able to stay still but it is important to keep on moving if you don’t want to get hit by the other bone attacks.
• Gaster Blasters:
  • Description: Sans will summon Gaster Blasters that fire beams in specific directions.
  • Strategy: The beams are quick but they usually have a set pattern. You will need to learn when they will shoot and adjust your movements accordingly. Sometimes, they will be placed in tight places so you will need to adjust your movements in anticipation of the attack.
• Platforming Segments:
  • Description: Sans will often introduce platforming elements during his attacks, forcing you to jump over bones and projectiles.
  • Strategy: Focus on timing your jumps carefully. Remember, you can use your invincibility frames to move through some attacks in mid-jump if needed. Try to maintain momentum and be ready to land and move to your next safe spot as fast as possible.

Phase 2: The Gauntlet

Phase 2 increases the complexity and density of Sans’ attacks, pushing your dodging skills to the limit.

• Bone Walls and Columns:
  • Description: Sans will create moving walls and columns of bones that will quickly surround you.
  • Strategy: This part of the battle is about quick decision making and movement, there are usually safe spots to get to, but you need to react fast to not get caught by the wall. Focus on finding gaps and move to them before they close.
• Rotating Bones and Blasters:
  • Description: Sans introduces rotating bone attacks and Gaster Blasters that move in circles.
  • Strategy: This attack can feel overwhelming at first but after a few tries you should be able to anticipate the movement of the bones and blasters. Try to stay near the center and move around when necessary.
• Rapid-Fire Bone Tosses:
  • Description: Sans increases the frequency and speed of bone tosses, making it harder to track individual projectiles.
  • Strategy: At this point, you may be relying on your invincibility frames more frequently. Keep moving and trust your instincts. Do not try to stop and move again since you will get hit if you try to do that.
• Combined Attacks:
  • Description: Sans will combine multiple types of attacks at once. For example, he may combine rotating bones with static bones and Gaster Blaster beams.
  • Strategy: Focus on identifying the biggest threat of each attack and move around that. You should be able to see openings that you can go to even with so many attacks coming to you. Do not panic and focus on your invincibility frames.

Phase 3: The Final Push

Phase 3 is a culmination of everything you’ve learned and represents Sans’ final stand. He’ll use a combination of familiar attacks with increased speed and intensity, plus some new surprises.

• Intensified Bone Attacks:
  • Description: All bone attacks are faster and more aggressive than before.
  • Strategy: Focus on your movements and try to stay calm. Every mistake you make can be costly, so you need to be hyper-focused. Use your invincibility frames when necessary.
• Gaster Blaster Barrage:
  • Description: Sans unleashes an overwhelming barrage of Gaster Blasters that will fill up most of the screen.
  • Strategy: There are small openings you can go to where you can avoid being hit by the beams. You will have to be quick and patient at the same time to be able to recognize these openings.
• The “Invisible” Walls:
  • Description: Sans introduces “invisible” walls that will block your movements. These walls appear quickly so you will have to be on the lookout for them.
  • Strategy: This attack is designed to throw you off balance. Try not to move too erratically and stay calm. Once you see the wall, try to quickly move around it or through it (using invincibility frames).
• The “Special Attack”:
  • Description: This is the hardest attack in the fight. It consists of a long stream of bones and Gaster Blasters in a combination that can be hard to dodge if you are not prepared for it.
  • Strategy: This attack is hard to react to, since it can change depending on what you do. What you need to do is keep moving forward and towards the center. If you stay calm and keep an eye on the Gaster Blasters, you should be able to avoid the bulk of the attack.

Specific Strategies and Tips

Here are some specific strategies that can help you during the fight:

• Memorize Attack Patterns: Sans’ attacks, though seemingly random, follow a pattern. The only way to learn these patterns is to keep on practicing.
• Practice Individual Segments: If you are having trouble with a particular attack, try to practice just that segment, without attempting the full battle.
• Don’t Be Afraid to Fail: This is one of the hardest fights in the game, you will die many times before you beat Sans. Do not get discouraged and try to learn from every death.
• Heal At the Right Time: Healing when you can is vital to staying alive. However, sometimes it is best to wait a bit before healing because you may get hit right after you heal. Learn when to use your items and when to wait.
• Take Breaks: This is a very long fight and it can be draining to keep on doing it. Try taking a short break if you feel like you need to.
• Patience and Persistence: This is a fight of attrition, you will be tested. Do not lose hope and try to take each attack as a learning opportunity.

The “Mercy” Option and the Final Act

Once Sans is tired, and his health bar is empty, he will give you an option to spare him or not. However, if you choose to spare him, he will instantly kill you, starting the entire battle over again. The only way to end the fight is to attack when he offers the Mercy option. Even though the text will prompt you to spare him, attacking him is the only way to proceed. After this, Sans will finally accept defeat, letting you continue on your path.

Conclusion

Beating Sans in Undertale is a monumental achievement that requires skill, patience, and a deep understanding of the game. Don’t be discouraged by the difficulty, and keep on practicing. By memorizing his patterns, mastering your dodging skills, and utilizing the tips and strategies outlined in this guide, you can overcome this final hurdle and complete the Genocide Route. This fight is designed to be challenging, but the satisfaction of finally achieving victory makes all the effort worthwhile.

Remember, the battle against Sans is not just a difficult boss fight, it is an emotional and thematic conclusion to the story of the Genocide Route. It’s a test of your commitment to a destructive path, and it’s a testament to the power of perseverance.