These secret techniques were actually all based on the Controller's internal universe. They unleashed their speed through the use of the internal universe or worlds.
Lin Feng analyzed it carefully and excluded those secret techniques that required a large number of worlds as the foundation. At least for the time being, they were not suitable for him. Actually, he was more willing to choose a secret technique which could increase his speed as his strength improved, and his number of worlds increased.
It would be a developing secret technique. This way, the range of selection was much smaller.
The power of such secret techniques was actually similar. Moreover, the principle was the same. They all possessed extremely fast speed through the contraction and eruption of the internal world.
Some were relatively enduring, while others focused on instantaneous eruptions.