DELTARUNE: How to Beat the Secret Boss (Chapter 3, 4)

When you get into a TV show, you have to finish it in the S rank. Then go in the S-rank room Then go left and talk with NPC, get into the room and play the game in the left side. Don’t worry, killing enemies don’t ruin pacifist run (i think, if you worry you can do backup). When you are MAX LV, find a room with lots of trees and chop through. Up, you will find chest with ICE KEY.

Then you must finish round 2 in the S-rank. Do the same thing, when you kill every enemy, go to the raft and sail to the waterfall. Go through the waterfall. Then go left and up, to the north. You’ll see white stones, find a wharf and go to the door. Open it with ICE KEY. Kill every enemy in the dungeon (which you can kill) and find white cloack. When you attack, it freeze enemy, so use it for puzzles. When you freeze bird (it’s nearby enterance), go right and “follow the white cloack”, it will follow you only when you get on the right way (you’ll see). Finish the game, and wait when you can come back into this room (it’ll be in the end of the chapter)

When you come back, go to the room and start the game.
Kill your friends in the game to gain LV and break the road barriers on your right.
Then, all in your hands, finish the game, kill “The boss”, and loot Shadow Mantle from chest.
Wear it (Prefer Susie).
In fight with Knight charachter with Mantle will get less damage.
So, survive Knight’s attacks and loot your shadow cristall before run.
Congratulations!

Firstly, you must get a ClaimbCrawl when you beat Jack (it’s regular boss). Then follow this steps OR I’ll pin notes in the end of guide, you can use it (i don’t know how it’ll work):

You’ll find waterfall, behind it will be door (if not, donate in the lake)
In the end of room climb (click Z), go through and find notes, then run, watch cutscene and go to study

When you back to the study, go to south. Go left, and find the tower in the room with lanters and moving things which damage you. Climb on it,

Climb, and then find a water. Interact with it and go away, you’ll be attacked by Cooler. Fight with it and get notes.

Go right, to the checkpoint nearby the place where you find old man. Climb on the last tower, solve little puzzle and get last notes!

Go to the library and climb to the top of it, You’ll find a piano, play notes, so, you opened room, Congratulations