To spare Undyne, you need to survive her waves of attacks until she changes your heart back to red and throw a spear at you.

Run during this turn.

When you get on the overworld map, Undyne will be stunned for a moment. Use this to run upwards. She will catch up with you and will attack you again. Keep running when your heart is turned to red again. You need to do this three times in total.

After three waves, Undyne will no longer turn your heart green. At this moment on just run all the way to Hotland. Around halfway on the screen that displays "Welcome to Hotland", Papyrus will call you (if you spared him), giving you a moment to relax. Undyne will not move during the phone call.

On the first screen of Hotland, you have a few additional seconds because she will stop for a moment and get angry at Sans.

She will collapse on the next screen, because her armor overheats. If you want to befriend her later on you need to give her water from the nearby water cooler.

There are two ways to SPARE Muffet.

Option 1: Spider Bake Sale

If you buy an item from either of the two Spider Bake sales (Spider Donut or the Spider Cider) and use it in battle, Muffet can be SPAREd instantly without having to fight her.

There are two Bake Sales in the game. The first can be found in the Ruins and is the cheaper of the two, with the Donut only costing 7G and the Cider 18G. In the CORE, both will cost 9999G.

Option 2: Wait her out.

If you have to SPARE Muffet manually (because you couldn't afford the Donut or the Cider), you need to wait long enough (17 turns) until Muffet receives a telegram from the spiders in the Ruins who will explain that you are not evil to spiders.

Here are some pointers for the Muffet fight if you need to wait her out.

• Muffet's first attack is to turn your heart purple. Don't pay her anything. It is a waste of cash at this turn.
• The trick in this fight is to look at the sign that is held up while it's your turn. It will either show a spider, two spiders, a Donut or a Croissant (boomerang).
  • If the sign is a spider, she will send a pattern based style attack at you. Two spiders means that the amount of spiders will be larger.
  • If the sign is a Donut, she will throw Donuts at you instead. The Donuts do not follow the lines of the web and bounce around the box.
  • If the sign is a Croissant, she will throw Croissants at you. The croissants will make to about a third of the battle box and then return the same path.
• By far Muffet's most dangerous attack is her summoning her 'pet'. This will occur three times during the battle. First the battle box will begin to move to the left, whilst spiders come across in the shape of a pattern. After that her 'pet' will appear on the bottom of the screen and will begin to consume the web. Keep moving upwards, all the while dodging spiders.
• Paying Muffet halves her damage for one turn. The price increases with each turn paid.
• Struggling three times makes Muffet halves the price to pay her. This can only be done once and the effect only lasts one turn.