Undertale: Sans Fight Guide
This guide contains Undertale spoilers for the no-mercy run! Don’t read it unless you’ve played Undertale, and tried to fight Sans at least 30 times!!!
… Ok so you’ve tried to fight Sans at the end of no-mercy run, and you failed a whole bunch, right? Then this guide is for you. If you’re having trouble on specific attacks, Sections 2 and 3 should help. If you’re having trouble in general, sections 0 and 1 will be the best reads. If this is going to be your first time beating Sans, you should read section 4 anyway.
All gifs were made at giphy.com from a run I did.
Sans battle is extremely difficult. It’s especially designed to make you want to quit. It’s designed to test your determination. It’s designed to make you WANT to do anything other than win. This guide is, effectively, a determination guide. There are a couple tips you might want to consider.
You’re going to get worse. Before you win, somewhere around your 20th try, you’re going to start getting worse. You’ll start dying on easy attacks. Your fingers will cramp. You’ll forget what happens next, or even what you’re doing. You’ll start to space out. You’ll feel like it isn’t worth it anymore, and you want to quit.
If you are determined to do this, you can push through it. You’ll get better again.
It’s going to take forever. No matter how good you are, no matter how quickly you learn, this is going to take a long time. It’s going to feel like an eternity. Every battle will feel like a day and a half. You’ll pick it up day after day and lose over and over again. You’ll want to stop after twenty tries, and you know it might take hundreds.
If you are determined to do this, don’t stop. Sans isn’t perfect. He has to trip up eventually.
You’re going to hate it. Nothing about this battle is fun. The reward for winning is worse than nonexistent. Everyone hates you for doing this, and you hate your self for killing them. The end you’re trying to obtain is sad and lonely and futile.
If you are determined to do this, ignore those feelings. The determination of a killer like you is enough.
Are you trying to fight sans with Cinnabuns? Well knock it off. There’s a couple good foods you can keep that will massively help you with your battle.
Butterscotch Cinnamon Pie: Full heal. You get this from Toriel at the beginning of the game iff you take a nap in the room she gives you. If you didn’t take a nap, you blew it. If you ate it already, you blew it. If you still have it, though, it’s indispensable for this battle.
Instant Noodles: 90 HP. You get these from Alphys’s fridge in her lab, but you can only take one. In the no-mercy run, you eat them dry, making them heal more than in a pacifist run. If you don’t have the ‘Bscotch pie, this is your next best bet.
Steak in the Shape of Mettaton’s Face: Heals 60 HP. You can only get one, and it’s purchased from Burgerpants in the cafe before entering The Core, it’s in the same room as the Mettaton Fountain, to the upper right. If you don’t have the previous two, you need this. You’ll need to save up your money for it, but that shouldn’t be an issue unless you’ve somehow wasted your cash.
Snowman Piece: Heals 45 HP. You get these from disassembling (killing) the snowman back in Snowdin. You can have as many as three pieces. If you don’t have them though, don’t worry about it, the following item is almost just as good.
Legendary Hero: Heals 40 HP. The rest of your entire inventory should be filled with these. They can be purchased from the same place as the Face Steak, but you can buy as many as you want. If you somehow wasted all the above items, this is your last ditch effort.
Gear: As for armor and weapons, there’s not much you can actually do. Burnt Pan might help a little? Most of the effects are negated or useless, because Sans bypasses defense, avoids all attacks, and ignores INV. I honestly don’t think what you use matters at all.
2. First Half Attack Patterns
The Sans battle is extremely fast. Knowing what’s going to happen before it happens is going to help a LOT. I’ve categorized the attacks and given them all names so you can remember what to do.
In the first half, there are 10 unique attacks of varying types.
The Strongest Attack
Qualities: One type. Appears only once. First attack. Lasers. Blue soul. Red soul.
This is the first attack is the first attack. Sans slams you down, shoots bones at you from the floor, splashes a bone wave at you, and sends you through four sets of lasers.
Peculiarities: The first time you fight him, the attack is triggered when he finishes saying “SHOULD BE BURNING IN HELL”. The second time you fight him, he tries to trip you up by ending his dialogue out of turn, at “Birds are singing…”. All times after that, he attacks when you finish “On days like these, kids like you…”. If you jump slightly too soon after he slams you down, you will land in the bones on the way down. There’s a slight lip downward at the end of the Bone Wave, so if you don’t move down, you’ll nick it.
Tips: Saying “On, off” for when each laser set starts and ends helps me keep time and not move too early or too late. Moving into the lasers is as much a threat as not moving out of them.
Jump Rope
Qualities: Vertical. One type. Reoccurring. First appears as second attack. Blue soul.
During this attack, you are attacked by colliding bone columns with a small gap at the bottom.
Tips: You have to make eight short jumps in rhythm. It’s named not only because of the motion you need to make, but also because saying “Jump, Rope” out loud, rhythmically, can help you keep time. DO NOT MOVE LEFT OR RIGHT.
Blue Bones
Qualities: Horizontal. One type. Appears only once. Third attack. Blue attacks. Blue soul.
This attack throws six pairs of one short white bone, and one tall blue bone. The first three pairs come from the right moving left, the next three come from the left moving right.
Peculiarities: The fourth set comes very quickly after the third set, from the opposite direction. Be prepared to move the opposite direction almost immediately.
Tips: The best way to do this is to make very short jumps over the short bones while also moving in the same direction as them, away from the blue bone, and then stopping when you touch the ground until the blue bone passes, and jumping again immediately after. The shorter your jump is, the less horizontal space you’ll waste. It is in short supply.
The Crusher
Qualities: Vertical. Randomized. Reoccurring. First appears as fourth attack. Blue soul.
This attack is similar to Jump Rope, except the number of attacks and the height of the gap is random.
Peculiarities: Higher gaps are slower, lower gaps are faster, and the more faster sets there are, the more sets there will be in total. It is generally slower than Jump Rope. Sometimes one of the columns is faster than its pair, but it starts later such that they always meet in the center.
Tips: Pick one side to focus on. Watch for when a column comes from that side, and when you check its gap height, look at your soul while jumping to square in the perfect height. You can ignore the other side because the two sides always converge at the same time. DO NOT MOVE LEFT OR RIGHT.
Lefty Solo
Qualities: Horizontal. One type. Appears only once. Fifth attack. Platforming. Blue soul.
A pool of bones approaches from the left, and on top are several platforms.
Peculiarities: The final platform has a bone block above it you will hit if you jump too high or too late. The bone pool stops after the third platform, but if you don’t jump off, a bone will swipe you.
Tips: As long as you don’t fall off, this should be no problem. Jumping as early as possible will circumvent the peculiarities of this attack.
Righty Solo
Qualities: Horizontal. One type. Appears only once. Sixth attack. Platforming. Blue soul.
After Lefty solo comes this one. It’s similar in style, but it has more peculiarities.
Peculiarities: Bones above and below various platforms requires you to land on almost all of them, no skipping. At the end, a bone comes in from the left, but it is merely a distraction from a second bone coming from the right.
Tips: You must jump over the second platform, but you can immediately land on the third (sliding off the second is slower). You can short your jumps by slowing down just before landing to avoid ceiling bones. You can slide down to the fifth platform instead of jumping. If you hard jump up+right as soon as the last rightward bone appears, you always land safely.
Bone Platforms
Qualities: Vertical. Randomized. Reoccurring. First appears as seventh attack. Platforming. Blue soul.
This attack throws you in with two layers of platforms moving left and right, and three layers of bones which follow the movement of the platforms above them (the top row follows the bottom row).
Peculiarities: Sliding on platforms slows you down, but you move faster on the floor. You move slightly faster than the bones sliding on the floor, and slightly slower than the bones sliding on the platforms. You can’t see the bones until they enter the box. The upper platforms are longer but have bigger gaps than the lower ones.
Tips: Stay on the floor as much as possible, and make short bunny hops when on the platforms to maximize mobility . Staying in the middle of the area will prevent you from getting hit by bones that come in from the walls where you can’t see them. The long upper platforms can allow a good alternative when in a pinch, but because the gaps are further apart, it’s an investment that might trap you.
Monorail
Qualities: Horizontal. Two types. Appears twice. Eighth attack (JSS) and tenth attack (SSJ). Platforming. Blue soul.
This attack starts you on a platform on the left of the screen. The platform moves through three columns of bones to the right end, then back again to the left.
Peculiarities: The middle column moves down while the outer two move up. The middle column has bigger gaps than the outer, but the gaps are irregular in size.
Tips: While moving right, you can always slide past two columns. The first type of this attack requires Jump Slide right Slide right (JSS) , and the second requires Slide right Slide left Jump (SSJ). You can always slide past the first two columns when moving backwards, slide right for JSS and slide left for SSJ. If you jump in between the last two columns moving left, the attack ends before you land, avoiding the final column.
Laser Platforms
Qualities: Vertical. Randomized. Reoccurring. First appears as ninth attack. Platforming. Lasers. Blue soul.
This attack is similar to the bone Platforms, but instead of bones, it’s lasers, which attack an entire layer at a time
Peculiarities: You slide slower on the platforms. The upper and lower platforms are the same size, but the gaps are bigger on the upper platforms. This attack gets faster after the first time. The most the same level will be attacked in a row seems to be three.
Tips: Like with bone platforms, it’s easier to say near the bottom to maximize mobility. When a laser aims at the bottom, jump to one of the edge of a platform in the first row, then wait for the lasers to stop firing at the bottom, and slide off. Stick near the right side during this tactic, because occasionally three lasers will attack the bottom in a row, and you need to maximize your potential travel distance.
Pockets
Qualities: Horizontal. One type. Reoccurring. First appears as twelfth attack. Blue soul.
This attack has short bones approach from the left on the ground, and tall bones approach from the right on the ceiling.
Tips: Move to the right wall as soon as you recognize this attack. You can jump through the pockets in rhythm repeatedly. It’s possible to skip multiple pockets with higher jumps and better timing (Minimum jumps by pocket skipping is two).
Order of attacks:
During the first half of the battle, there are 13 lines of dialogue that need to be passed, and it can only be advanced by FIGHTing. Coincidentally, the first 13 attacks are always the same ones:
Strongest -> Jump Rope -> Blue bones -> Crusher -> Lefty solo -> Righty solo -> Bone platforms -> Monorail (JSS) -> Laser platforms -> Monorail (SSJ) -> Jump Rope -> Pockets -> Crusher
This might be hard to remember, but there’s an easier pattern that has to do with the movement types:
Strongest -> Vertical -> Horizontal -> Vertical -> Horizontal (L) -> Horizontal ® -> Vertical -> Horizontal -> Vertical -> Horizontal -> Vertical -> Horizontal -> Vertical
That is, after the first attack, the first 13 attacks are in directional type pairs, which are based on the dominant directions of movement. This will give you a leg up if you don’t remember what exactly happens next.
First half general tips:
There are only 13 lines of dialogue after Sans finishes the first attack, the only way to advance is to fight, which means you must attack Sans 14 times in order to get to the half-way point. When Sans says “Seeing what’s happening next, I can’t afford not to care anymore”, you’ve effectively finished the first half. The next time you attack, Sans will spare you instead of attacking, giving you an infinite number of free turns to do anything besides attack (I.E. heal). If you can avoid healing until this point, you will minimize the number of attacks you will have to go through, thus maximizing how much food you have left for the second half. If you Spare Sans, you will get dunked on, fair warning. This guide is much longer than I thought it would be. That’s one of the tips.
3. Second Half Attack Patterns
Now the real battle begins. The second half is much more difficult than the first half. There is no rest here, you can not pause, the fight is unending. If you paused during the second half to read this guide, you’re probably dead.
In the second half, there are 5 unique attacks of varying types.
Clips
Qualities: Two type randomized. Reoccurring. First appears as first attack. Blue attacks. Teleportation. Blue soul. Red soul.
This attack teleports you in the middle of various attacks extremely quickly.
Peculiarities: The entire attack.
Tips TYPE A: Composed of four peculiarities, all blue soul. Jail, which demands you to max jump as soon as possible. Blue jail, which requires you to max jump as slow as possible. Fringe, which requires you to max jump and then move toward the center. And two, generally low sets from The Crusher, as mentioned in section 2.
Tips TYPE B: Composed of four peculiarities, half blue soul half red soul. Bone Wave, as in the first attack of the battle (red). Quad Lasers, either diagonal or horizontal, requiring you to move to the edge, or to the corner (red). Diamond, which requires you to drop down from one platform to the one below it in a particular direction, and then jump back to the top platform from the opposite side (blue). And a clip from the middle of Pockets, as mentioned in section 1 (blue).
Tips: Recognizing which type you’re doing is instrumental. The attack is extremely quick and chaotic.
Meta Bones
They attack you in the menu. Try to remember what option you last left off on from the previous attack, since you will start where you last used. Get into the habit of pretending the menu bones are there from the beginning of the second half, the rhythm is always the same, so it will help you improve muscle memory. Take your time in the menus, but not too much time.
EGG
Qualities: Randomized. Reoccurring. First appears as second attack. Lasers. Red soul.
What does EGG stand for? Evil Guided Gasterblasters. This attack summons various lasers around a rather large area which lock on to your location when they’re summoned.
Peculiarities: Lasers are half size for the first attack.
Tips: Watch each laser as it arrives. Check where it’s pointing, and commit to a direction to go. Try not to turn more than 90 degrees, or you might run into a previously avoided laser. You need to really commit to a direction, don’t change your mind half way because it got harder. Don’t be afraid to stop moving for the duration of one laser if you get cornered, but get out immediately after. In general, you’ll end up moving in wide circular paths, that’s pretty optimal.
Slam
Qualities: Randomized. Reoccurring. First appears as fourth attack. Blue soul.
Easily second hardest attack to do perfectly, Sans slams you into various walls over and over.
Peculiarities: Gets faster after the first time, and then ridiculously fast after the second time.
Tips: Watch his hand, not your soul. Ignore your soul and look at what Sans is doing. You need to jump off the wall the instant you touch it, you can’t waste a single moment, which means you need to be holding the right key before you even get there. The only way this is possible is to watch his hand, his hand is a tell much more quickly than the actual attack.
Be The Leaf
Qualities: One type. Appears only once. Seventh attack. Red soul.
In this attack, two rows of bones move in opposite directions up or down, and meet in the center of the box.
Tips: Move near the top or bottom of the box, and spin in smol circles. BE THE LEAF.
Last Attack
Qualities: One type randomized. Appears only once. Last attack. Lasers. Teleportation. Blue soul. Red soul. Longest attack.
This is the last attack before the Special Attack. It is composed of eight basic parts: Four Slams, half of Be The Leaf, about four sets of Bone Wave, nine blocks of bones you need to zig zag through, a bone funnel, four sets of wall jumps two of which are corners, a spinning laser focus, and thirty six declawed slams in a row.
Peculiarities: After zig zag, if you jump immediately on the first two slams, you’ll fall back into the bones, but you can jump immediately on the second two sets. The spinning laser focus gets increasingly faster over time. If you push against the walls after Laser Focus, you lose health faster, but you still can’t die.
Tips: The first two parts are previous attacks in the second half. Saying “Bone wave” rhythmically during the Bone wave segment can help you keep on rhythm. The zig zag portion is virtually identical to Bone Wave, but requires boxier, less fluid movement. Funnel simply requires you to be in the center after zig zag. During the corner jumps, you can jump immediately and survive fine. Start near the bottom right of the screen for laser focus, moving in straight lines makes you slower and offers more control. As the focus spins faster, move your box closer to the center. After the laser focus, the 36 slams deal 1 damage each, or 0 damage if you are at 1 hp, thus you are likely to be at 1 hp at the end of the battle. You can’t die after the Spinning Laser Focus.
Once you finish the last attack, Sans uses his Special Attack, the most powerful thing of all. If you wait long enough, skipping his dialogue, eventually he falls asleep, and you can move the combat box to the FIGHT option out of turn by pushing into the lower left corner, ending the attack.
Peculiarities: If you touch the left wall before Sans falls asleep, you’re teleported to the center of the box and Sans is wide awake again, making you waste more time.
Tips: It takes about six entire minutes of waiting, so while you’re getting ready to kill this skeleton, you might want to take a moment to consider when to give up. Did you do all this because it was hard? Because you wanted to show how determined you could be? Well you did. It’s a beautiful day to throw a party for all the friends you murdered. And to quit.
Or instead, did you just want to see what would happen? Did you do all this just to see every ending? Every line of dialogue? Every possibility? Because you were bored. Because you didn’t feel anything for the characters anymore. Just because you thought you could do it without consequence, did you have to? You can’t afford not to care anymore.
There’s nothing left after this.
