Redan, also known as the Lightning Pill, is a compressed baang of Shinsu, the current of which, after swallowing it, reacts with the current in the user's own body, generating explosive power. The technique can only be used by a few selected members of the Khun Family.
This is a technique that increases the power of its users; in Ran's case it's a baang with electrical properties that makes electric currents flow through his body, thus increasing his strength and speed.
This technique is extremely hard to control; even Ran can only control it for 5 minutes. Additionally, the data of young Khun Eduan himself described the technique as simple and effective but dangerous at the same time which does not make it a good skill to use.