You exhale heavily. "Well, the truth is that teaching this stuff is normally supposed to be a very slow process. Something like one or two years to learn the basics of how to shield, and then a couple years on tunneling. The reason being that tunneling can be dangerous. You can end up somewhere you didn't mean to, or the walls of tunnel can damage you. The shield is supposed to protect you from the volatile energy that forms on the walls of the tunnel, so it's very important to have a good shield before trying to tunnel."
"hmm...makes sense."
You think that's all he's going to say for a moment, but then he seems to make a decision to speak freely, even though the information he shares next is clearly important to him.
"when i do a shortcut in my world, it's more like hacking. the base reality of our world is code, so i have to actually rewrite the code with magic. but there's some things it won't ever let me do, like reset, or travel beyond our world's boundaries, or leave the underground without the barrier being down. it gives me what you might call an access denied error message."
Thoughtfully, he makes drawings in the air, three dimensional ones this time, as you watch him mentally work through concepts. The first sketch gives you a rough idea of what shortcutting looks like, showing how he rewrites code to allow him to connect the spatial coordinates of two different places, creating a temporary doorway between them.
"so i wonder, when you tunnel, are you having to break rules like me...or do you use a set of rules that works across worlds?"
He makes his second drawing show two spheres being connected by a tunnel.
"The second," you say. "There's a set of rules that overrides the laws of worlds. Actually, not exactly override, that's not the best way to say it. It's more like they are base rules that work no matter where you are, whether you are in a world or between. Souls themselves have an existence outside of worlds, so by accessing the deepest levels of the soul, you can access those rules. If you're imaginative, creative, and compassionate, it's easier to do it. If you're an evil person, it's very difficult if not impossible to do it on your own power, since evil people generally hate themselves and don't want to face what they really think of themselves on a conscious level."
He looks at you curiously, as he considers that carefully, and eventually he lets the midair drawing fade, possibly feeling overwhelmed by the scope of what he doesn't know.
But his eye lights are sparkling, and you get the sense that he really deeply enjoys learning new things. Maybe the chance to learn new things doesn't come nearly often enough for him, being trapped in the timeline resets for so long the way he is.
"hmm. m' glad to hear it's harder for bad people. got a ton of questions about that, but we don't have a lot of time. if it usually takes years to learn how to tunnel, do ya honestly think there's much hope i can do it in a week?"
"Well, the fact that you were able to use mental abilities so well by showing me part of your past gives me a lot of hope. You were also able to figure out both how to start and end a mental connection with me completely on your own. I think traditionally it would probably take too long, yes...but given your talent at it, maybe if we make that mental connection again, I can do a sort of download of all the information on how to shield and tunnel. It could be really overwhelming for you, so we'll have to be careful about how we do it. But if we take it slow and steady, I believe there's a solid chance that you can do it."
He sighs wistfully. "wish your hopes didn't have to rest on me, but i'll try, whenever you're ready. what, do you want me to sing something again?"
"Well, yeah," you say, grinning awkwardly. "That's how me and another one of my people do it usually. We sing and try to match each other's melodies, and we focus on making a mental connection. It should be easier than when you had to do it on your own, when I was unconscious."
"I wonder how you are at singing by ear?" you ask thoughtfully.
He grins. "actually, i play instruments by ear sometimes when i'm alone. we used to have a jazz band that was pretty good. we could jam with anyone from the crowd who wanted to start us off with a song. that kinda all went away when no one wanted to do it anymore after..." he trails off sadly as his eye lights look misty and soft, and you can guess the rest on your own. It went away when the resets started.
"I'm sorry..."
"s'ok, i'd mostly forgotten about it until now anyway."
"Did you play some brass maybe?"
"yeah, sax and trombone, among others," he says shyly. "i like the brass and woodwind instruments."
"That's awesome."
He shrugs sheepishly. "i'm not much for singing usually, but i'll try. just let me know when you're ready."
You grin encouragingly. "All right. Here goes."
You make sure you're both comfortable lying down next to each other on your backs, and then start to sing, vocalizing a melody.
Despite what he said about not being much for singing, he has a soft yet deep voice with some amazing bass overtones. He's able to follow what you sing quite well. You can tell he has a musician's background by the way he improvises against the basic melody.
Gradually, you pull both of you back into the kind of mental space you were in before, imagining a peaceful area by a lake to start with.
You start out by showing him your memories of Aldyr teaching you how to shield and tunnel from your past. Then you move on to when you were practicing, showing him what seemed to work and what didn't. You try not to overload him, but Sans is amazingly fast at picking up the information and understanding it. Eventually, you realize you don't have to slow yourself down for him. He can understand the information as fast as you can show it to him.
You quickly realize that, like you suspected before, he's really far more intelligent than you are. It becomes obvious to you that most of the time in casual conversation, he's pretending to not be as quick at understanding things as he really is. Was this something he just learned to do over time, to make it easier to get along with people by not annoying them by being a know-it-all? Could it also be an act he learned to put on with humans like Frisk and Chara, to keep them off guard?
In any case, he's obviously had his defenses up with you too. You wonder what he would be like if he were being completely honest with you. Maybe the excitement you're seeing from him now while he's learning all of this new stuff is a peek at the real Sans. You like it, but wonder if you'll get to see this side of him in the future, or if he'll hide it again as soon as you've broken this mental connection. The thought makes you a little sad.
Once you've "shown" him the basics of accessing and using Eldorant abilities with your mental connection, you try to communicate to him without words the core of everything, how to access the deepest parts of the soul. It's not easy, but without being able to do this, you know that nothing else will work. Doing it for the first time is the hardest part of learning how to use Eldorant abilities. It's so difficult that you've never met another group of people who know how to do it, in all of your time exploring other worlds and universes.
Here is where you see him truly hesitate for the first time. You're not sure if he doesn't get what you're trying to explain, or if he's hesitating for another reason. You know it's a very difficult topic to understand in any case, so you're not going to push him to understand it all right away. After showing him how to do it as best you can, you break the mental connection and bring both of you back to consciousness so he can practice on his own.
Given how fast he picked up everything, you hoped him actually accessing and using Eldorant abilities for the first time would not take him too long. It's a bit unfair, you know, as most people take much longer than a week to do it, but he learned everything else so fast that you have unusually high expectations of him being able to pass this final hurdle quickly.
But to your surprise, even after several hours of practicing, he still can't create a shield of his own. Sometimes he creates sphere-like magical barriers, but he knows that's not the same thing as using the shielding ability like the way you showed him. He looks annoyed with himself as he stands there with his hands in his jacket pockets, his jaw tense.
"sorry. maybe you're better off not counting on me," he says, noticing you watching him from your sitting position on the ground. "sure your abilities are still broken?"
"Yeah, I think so, unfortunately. I'm still trying though."
He sighs. "been doing what you showed me, and imagining creating a shield, but it's still not working. maybe i'm doing something wrong. i keep trying to do it with magic, but this is something completely different. you don't use magic at all, right? i haven't sensed any."
You nod. You've told him all you could. You don't know why it's not working. At this point, he has to find the answers himself.
"maybe i have to think more in terms of what about our souls is the same to find the answer. what things are the same for both monster and human souls? is there something basic about my soul that's making it harder for me than it is for you?"
He pauses, thinking for several minutes. You stay silent so you don't distract him.
"maybe it's not about species...maybe it's more to do with our different experiences in life. you've had it pretty rough, but your soul hasn't been broken like mine has...maybe the problem has something to do with my split soul. i can't access the deepest parts of my soul like this."
You tilt your head curiously at him, not understanding.
He glances at you, and you see determination in his eye lights.
"i want to try something. can i create a mental space on my own?"
"Uh, sure, you just do the same thing we did before, but focus on doing it inside your head instead of singing aloud. Imagine making a connection with a deeper part of yourself instead of with another person. Then you can create your own mental space. Don't forget that you have a body to take care of though, since you're probably not putting yourself in stasis mode the way I did. It's important to not stay unconscious for too long."
"ok, i'm gonna try that," he says, sitting down cross-legged. "give me a couple hours. can you pull me out of it after that, if it looks like it's going on too long?"
"Sure, will do." You still aren't completely certain what he's trying, but you hope he's had a good idea.
"thanks," Sans replies with a slight grin.
You see him close his eye sockets and focus for awhile, until abruptly he falls over on his side unconscious, his bones clattering on the hard rock of the ground. You wince. You should've probably asked him to lie down first or something, since he might lose consciousness faster than just falling asleep normally. It had been in the back of your mind, but the thought didn't coalesce in time.
He's not used to doing things like this, and you tell yourself that you need to be more cautious and not forget that. Hopefully falling over from a sitting position didn't hurt him too much.
You crawl over to him on your hands and knees, and carefully untangle his limbs. You make sure his skull is resting on the jacket sleeve on one of his arms like a pillow, so he'll be more comfortable lying down. Then you settle back cross-legged down nearby, expecting a long wait.
Your eyelids are heavy and you blink slowly, but you're determined not to fall asleep, despite how tired and weak you are.
One of the Gaster Blasters goes to inspect Sans, nudging him, and then floats over to you and emits a small questioning whimper.
"He'll be ok," you tell it, rubbing its bony snout while its white eyelights look up at you in a puppy-dog way.
"Can you help me stay awake?" you ask it. "We'll keep watch together, alrite? I think he's doing something important while he's asleep. But we have to make sure he's ok, even if it takes a long time before he wakes up. Can you please let me know if anything changes with him?"
It nods by moving up and down in midair, and gives you a soft whine that you interpret as a yes. It turns in mid-air and you get the sense it's having a short conversation with the other Blasters in a language you can't understand. One of them helps the first one to guard Sans, both of them keeping a very close watch over him with their large white eye lights. Two others keep their snouts pointed outward to continue to guard against outside threats.
At least with them here, you're not alone in your guard duties, and that is extremely comforting.
Your dry throat and hungry stomach gnaw at you distractingly, and the silence is making you sleepy, but you do your best to stay alert while you and the Gaster Blasters watch over Sans.