First up, I wanted to save the vids I took of my classes on the 'superhero landing' posture inside guard. I labelled it as 'superhero pose' on the vids, as that's one syllable less: not sure which one I prefer yet. The former is more descriptive, the latter is quicker to say. Anyway, I learned it from Chris Paines at the Artemis BJJ München Camp 2023 (I'll most likely do more camps there, in which case you can book them here). It is a posture I can remember Priit showing at one of his mega long weekend seminars at Chris' gym a few years back. As it was Priit, I found the explanation confusing and it never really stuck, despite several hours of Priit lectures.
Chris is an excellent Priit translator. In the space of about a minute, he was able to condense that down and make it very easy to understand. I've tried to continue that process, so I'm slapping a hopefully evocative name on it, with a few simple points to explain the mechanics. I called it superhero landing because it looks much like the pose you always see superheroes do when they hit the floor after flying in to stop the villain. Specifically, that's a three point landing (I guess technically four, but mainly three): hand, foot, knee. You can argue the foot of the knee leg makes it four points, but there isn't much weight on the foot back there.
That same position works surprisingly well inside guard, with a few tweaks. Imagine there is a stick running from the top of your head to your tailbone, that needs to stay in alignment. You also want to keep everything pointed forwards, particularly your knees. The hand on the ground breaks the usual rule of guard top that you don't put your hand on the mat. However, because of the positioning and alignment, you are putting all your weight through that arm, meaning it way less vulnerable to kimura and the like.
The hand also doesn't have to be on the mat (I'll often base off my fist, that feels more comfortable). You can put that hand on their collar, or probably the best of all, on their arm pinning it to the mat. Another good option is getting that arm by their head, if you manage to move up their body enough. You can then effectively cross-face them by placing it tight enough to their head to drive their ear towards their shoulder, misaligning the spine.
Chris told us at the camp that he's had his gym do this and pretty much nothing else for about 2 years. That has resulted in everybody having to get much better at guard, because you have to work harder to break it down when somebody gets good at using this posture. I'm planning to incorporate this into my classes on passing, eventually I'll work it up into a seminar I can teach at camps. It combines well with how I already teach my passing intro, so I think there's plenty of scope to play with it more.