I have an interest not just in Taekwondo patterns, but in Korean forms in general. Before the name "Taekwondo" was invented, the art was known as Tang Soo Do ("Chinese Hand Way"), and there are still organizations that operate under that name. Some of them created their own patterns, just like taekwondo organizations did.
One key figure in early Taekwondo/Tang Soo Do history is Hwang Kee, the founder of the Moo Duk Kwan ("School of Martial Virtue"). Hwang Kee studied not just Karate but the native Korean art Taekkyon and some Chinese arts including Tai Chi Chuan. Modern Tang Soo Do mostly teaches Karate kata, but advanced students may learn the original patterns that Hwang Kee created. The ones that interest me are the seven Chil Sung or "Seven Star" hyung.
You can watch a video of the first pattern, Chil Sung Il Ro, below
You might notice it does not look like a typical karate kata. While karate movements such as the low block and lunge punch are there, so are "soft" movements reminiscent of Tai Chi. In fact, the first two movements are based on "ward off right" and "ward off left" from Tai Chi.
Does it have applications? Of course! Searching online for applications does not yield much, but if you know any Tai Chi the movements will be familiar to you. One application for the two opening movements is a strike to the opponent's solar plexus while pulling the arm, followed by an arm break.
If this break fails, we can use the next two movements to pull in the opponent's elbow while pushing out their forearm -- creating a shoulder lock -- and then use the lunge punch as a takedown.
What of the next movement, the turn into the low ridgehand guarding block? This is performed in a stance not found in karate.
While many interpret this movement as a throw, I don't think that's right. It looks like a leg scoop to me: attacking the opponent's right leg from outside. From here we can use the next movement as a knee break takedown, pushing down on the knee with our left palm. I have included Kenwa Mabuni's knee break technique from Karate-do Nyumon for comparison, although they are not quite done the same way: in Chil Sung Il Ro you grab with the right palm and press the knee with your left palm.
Why use such a strange stance? Because you are leaning behind the opponent to scoop up their leg, hence you lean your weight on your left leg.
I could go on longer, but the point is that just because the movements look foreign does not mean they don't have applications. Furthermore, the Chil Sung hyung appear to be constructed with the same rules as the Ch'ang Hon and kukki-taekwondo patterns.
My second e-book is still on the way. I found that just Chon-Ji and Dan-Gun was not enough material to justify an e-book, so I will be including Do-San as well.