Niman is for Jedi Sentinels i think. I think it tries to balance and combine Ataru and the other forms.
Form VI: Niman was the sixth form of the seven forms of lightsaber combat.
The Way of the Rancor or The Moderation Form, Form VI was the standard style at and around the time period of the Clone Wars and the Great Jedi Purge. This combat discipline was often called the "Diplomat's Form." Unfortunately, all of the Form VI practitioners at the Battle of Geonosis were killed. As a result, full masters of other lightsaber forms sometimes considered Form VI to be insufficiently demanding.
Form VI attempted to balance all elements of lightsaber combat, combining the Forms that came before into a less intensely demanding combat style. The result was that the users' skill in each individual area of lightsaber combat was relatively moderate - they did not excel in any one area. This broad generalization made Form VI well suited for diplomats, as they could spend their time training in the areas of politics and negotiation instead of combat training.
The form was named after Niman, the triumvirate of Kashi gods and was adopted from the Jar'Kai form of combat.