Nigu Sayaw (loosely translated from several languages into "black dance") was a form/technique of Lightsaber combat developed by Actias Nightorb during the Cold War. Nigu Sayaw was conceived by observing several traditional techniques used by the Sith and Jedi. Essentially, this form is a hybrid of Juyo, Ataru, Djem So, and Shien forms, borrowing from all of them and taking advantage of their strengths and weaknesses. Nigu Sayaw was designed to be applicable by anyone of significant force sensitivity, against any number of enemies or weapons.
The technique revolved around heavy use of telekinesis and force augmentation of the body. A Sith or Jedi seen using the form can be described as constantly and viciously making rapid movements, even appearing as though they are disappearing and reappearing several times a second. Using telekineses to effectively use the lightsaber as a boomerang was a large part of the form. These actions are almost always used in rapid succession, or followed up by force lightning, force grip, or force push. A major element was avoiding blocking lightsaber or blaster attacks with your own lightsaber, as it wastes a significant amount of energy better spent by leaping beside or behind the opponent and making several quick blows. A lightsaber user will be thrown off by these actions and feel too drained to deflect the coming blows.
Another element of the technique is constantly moving unexpectedly and quickly. Basically, dancing around the enemy almost gracefully, but also incredibly lethally. This can be compared to Shii-Cho form, letting the flow of the battle control your movements. Like Ataru form, the duelist will involve jumps and dashes, never letting an oppurtunity to strike pass. This can compensate for size and stature.
Nigu Sayaw, despite its efficiency, was only ever mastered by Actias and his followers, and was lost and forgotten until the Galactic Rebellion, where, shortly before the Battle of Endor, Sith Emperor Palpatine visited the ancient homeworld of the Sith, Korriban, or as it was called post Clone Wars, Moraband. Deep in the Sith Academy library, records of the Nigu Sayaw form sat and gathered dust for thousands of years. Palpatine attempted to study the form, but the documents were too vague and old fashioned for his liking, and gave up his research, thus ending all recorded use of the form.
Nigu Sayaw form is best applied against multiple force sensitive opponents.
For visual reference, the best and closest example to this form was Darth Sidious in his battle with Darth Maul and his brother, Savage Opress.