New Home

- After beating Mettaton EX, head north, watch small cut scenes, and proceed into the Castle. You’ll eventually get forced into a familiar-looking house, past two save points. There are ‘battles’ from this point on, but they’re not actually dangerous to you.

- There’s a Key in the kitchen, and if you head to the bedrooms you’ll find a Heart-Shaped Locket and a Worn Dagger in the first, both good equips Get these, ‘cause on this path you’re really gonna need them. The second Key is near the end of the hallway.

- Use the Keys to get into the basement. There’s a loooot of walking and a looooot of talking ahead. Eventually you’ll find an elevator - it will return you to the beginning, if you really feel like going that way - and a lit room with a save point.

- Partway down this corridor you’ll meet someone familiar, and you will be Judged. This little bit is crucial, because it takes all of your actions and decisions up to this point into account. It might not affect the outcome much, but if you play this game again… which you should… be prepared.

- There’s another save point before the king’s room. If you go right from here you’ll find a straaaange side chamber that will hint at another crucial plot point. Oh dear. Inside is… another save point… and then one final one, I swear. Go through the final gateway, and, when you’re ready, talk to the king.

King Asgore, ruler of the Underworld. Serious fight all around.
Asgore

The big man himself. Asgore is an appropriately brutal opponent, and you cannot Spare him. This is a fight to the death. Asgore relies on a series of fire-based bullet attacks to do most of his damage, as well as the occasional swipe of his enormous spear. You can expect the following while you whittle down his health:
  • He’ll swipe fireballs at you from his hands. These will home in on you from multiple angles. Move from north to south and back again to send them veering off in the wrong directions.
  • He’ll create helix-like strands of fireballs. Watch the patterns and slide between the strands when they weave outward. Move down a few spaces to avoid the next strand and stay safe.
  • He’ll rain fireballs down on you, as well as cause them to erupt on both sides of the box. Stay near the middle when you can.
  • He’ll create an enormous whirl of fireballs. They travel in lines; try to follow the counterclockwise motion of the lines. (I suck at this one, to be honest. There’s too much going on.)
  • He’ll use his spear to slash you. Asgore will telegraph his attacks when his eyes shine, and will do so in order of his incoming attacks. If they’re orange, move; if they’re blue, stay still.
  • He’ll send in large loops of fireballs that shrink as they move closer to the centre of the box. There are gaps in the loops; watch for these and move into a safe spot.
When Asgore reaches half of his health, a few of his attacks - particularly the loops with the gaps - will increase in speed. All you can do is keep up your strength and improve your reaction times accordingly. On the off chance you still have the Butterscotch Pie, use it here - Asgore will recognize the smell, and his Attack and Defence will go down. (I discovered this totally by accident. God is this game good.)

Once you beat Asgore you’ll receive the option to kill or spare him. Regardless of which choice you make, the game will crash… and when you reload, the real final battle begins.

Flowey, god of everything and all-around douchebag.
Flowey

I knew it. This fight is, to be frank, batshit insane. Flowey turns into an enormous freak-beast, and will pepper you with attacks from all sides, constantly. There’s no RPG stuff here, just plain-out dodging finesse. It’s difficult to suggest what to do - and honestly, there’s not much point, because your hands will get the gist of the battle after a while. You’re going to take hits, so don’t worry about it too much. The Fight icon will also appear periodically; hit it, but it will barely do anything to Flowey.

The key here is to survive until the ‘breaks’. Every now and then Flowey will vanish, and you’ll face off against what appears to be a mini game. These mini games will give you the chance to hit an Act button, and doing so will create restorative items aplenty. Use these to survive until the next round. Do this six times and, after a quick cut scene, Flowey’s defences will drop substantially. Healing items will begin dropping out of his mouth regularly, and the Fight icon will appear all the time. Keep hitting it until he goes down. It’ll take a while, but your victory is inevitable.

It’s also worth noting that you really can’t lose here. You can die, yes, and the game will immediately crash, but when you open it up again you’ll be right back where you left off. Keep trying and you will eventually win.

The Aftermath

Once Flowey goes down you’ll have the chance to kill or spare him. Choose as you wish, though you get a teensy bit extra if you let him go. You’ll also get some ending dialogue from the characters you spared, and the fate of the Underworld will change depending on who lived and who died.

If you’ve come down this road then you experienced Undertale’s ‘Neutral’ play through. This is the game most players will see on their first trip, and it happens if you kill anybody. This includes random enemies. It also happens if you Spare anybody. The ending changes, but the basic results are the same, regardless of how you progressed. If you leave Flowey alive, though, he will hint at another option…

There are two ‘extreme’ routes you can now take, starting the game over from scratch:
  • The first is the Pacifist route. In a Pacifist game you can’t kill anyone. This includes random monsters. If you kill anything you get shunted back onto the Neutral route for the rest of the game. The Pacifist route features the ‘happy’ ending, and, to some, the ‘true’ ending. 
  • The second is the Genocide route. In a Genocide game you kill everything. If you miss even a single creature you also get shunted back to a Neutral route. The majority of the game is easier if you try out Genocide, and you'll essentially skip most of the bosses... but it also houses the two most difficult encounters in all of Undertale. One will make you rip your hair out; the other is as patently unfair as battles get. If you manage to beat the Genocide route you'll also permanently change the end of subsequent games, which is... harsh.
Had fun? Time to start over. Even if you go the Neutral route again, though, you probably won’t find the same game waiting for you. People change. Just saying.

Part Six: Pacifist Route