This is a dead end. Determination isn't enough to solve the problem. Alphys' secret isn't much help.
What's left besides Sans' room? That's the only other place I've never been able to penetrate. I've already been everywhere else. And Sans is the only person I've never been able to get.
Things I know about Sans:
He's a skeleton. Obviously.
He's the laziest monster in the Underground.
He's the most dangerous monster in the Underground.
He can predict things that nobody could know without resetting.
He can't reset.
He can teleport, or something like it.
He knows if you reset, and how many times.
He loves jokes.
He loves Papyrus.
He won't stop you from killing Papyrus. Or anyone else.
This isn't helping, either. This is all old news.
What bothers me most is that Sans could easily control this entire world if he wanted to. He has the power. I've seen it. But he just sits around and cracks bad jokes. Why?
Imagine that. Having power and never wanting to use it. I guess that's what it's like to be Frisk.
Let's move on to the Core. There's nothing for me in the lab. Not unless I want to bring back a soulless Chara. And I'm not sure I should.
The Core.
I don't normally spend much time here. It's a pain to go anywhere that doesn't have soil in it. The heat is awful. And I've caught fire more than once here. Not a fun way to die.
The Core powers the Underground using magma. They just send steam down to the magma, bring it back after it's heated up, and then use the steam to heat up isobutane, which spins a turbine to create electricity. It's the only reason there's any light down here, besides those glowing crystals they used back in the early days.
It's also the only reason we have any weather out in Snowdin. The power plant takes lot of heat out of the ground, and the extra heat gets pumped out into Empty Land. That's where all the wind comes from, and that's why we have clouds and weather in Snowdin and Farmland.
The funny thing about the Core is that nobody knows who actually built it. We know the previous Royal Scientist, before Alphys, was the architect, but who was that? Asgore somehow doesn't know… even though he hired them.
The Core is one of the places where Sans tends to show up unannounced. I always thought it was because he was afraid somebody (that is, little old me) would tamper with the Core and shut down the Underground. But now I think there's a different reason.
The Core has some big machines in it. Maybe big enough to break open Sans' secret room.
I barely got out with my life. Sans wasn't the only one protecting this place. Alphys has lasers and lightning bolts everywhere. I never learned how to dodge them… I used to have Alphys disable the defenses when I wanted to look around. This is going to take time.
I should probably start studying this journal. I might have to re-write the whole thing, if I die in an accident here. The journal won't be around if I reset.
Flowey's Journal, Part 2:
All right. I think I have everything written back down. Even the stupid parts. I have the rest of eternity to work on this. I can afford the extra time, if it helps me remember.
So many resets. This place is a death trap. No wonder Alphys built robots to run the Core. It kills anybody else.
I've got a new weapon… some strange laser beam. It's pretty impressive. If this doesn't open up Sans' room, I don't know what will.
I found that Temmie again. It would be fun to try out the new machine against it. But it only has so much energy, and Sans' room is more important.
IT WORKED! It worked it worked it worked! Finally!
I'm waiting for the fire to go out. It's taking its time.
Sans' room. What a disappointment.
Old socks. A treadmill he probably never uses. A messed-up bed. And a little tornado full of trash, for some reason.
So this is the secret! A tiny tornado! Golly! I sure am glad I found this!
I don't believe this. He HAS to be hiding something here.
A key.
This had better open the door at the back. Because if this is a key to the room I just broke into, I'm going to be furious.