Double Focus also known as Multi Focus, was discovered by Vercidime-Yata as he trained his mind to resist tempering through Illusions or Mind Tricks. He'd learned to be able to split his focus, being able to put his full attention on more than one thing. The development played a large role in his expanding of Moving Meditation, making him able to use it whilst moving across a landscape or flying his ship through an asteroid field.
It also may have saved his life on Tatooine, alongside his use of Force Light, as he was both parrying the saber of the Dark Lord, Valus, but also deflecting shots from his army. He'd approached it as two communicating threads in a process, having been so indulged in technology in his Sentinel days.
Full Focus was something Vercidime'd apply after having mastered Double Focus. This way he could put all his focus on something, making the wanted effect greater or executed faster.
+Endurance
Training and fighting in many different climates, and of course, the amplification of his power through the Tsil Crystal had given Vercidime more Endurance. Double Focus also allowed him to recover some of his endurance during battle, making him last longer in combat. The ultimate effect was that the use of every power exhausted him less.
"Force Immersion was a specialized technique developed by the Fallanassi, by which a skilled user could immerse themselves in the White Current, rendering themselves undetectable by any means, organic, artificial, Force-based or otherwise. Only careful scrutiny could pierce the Immersion technique, and even then the weak-minded would remain oblivious to their presence, unless the Fallanassi in question interacted with the beings in question." ~Wookiepedia
Vercidime had learned about this technique a long time ago, in his studies as a Sentinel. It interested him after his Master had told him he might make a good Jedi Watchman. Vercidime had remembered it in all the time that followed, but it took him a very long time to master. Now, finally, he was able to render himself completely undetecable. Though it could be pierced, it was very unlikely anyone would be spending their time doing just that everywhere they went.
OOC: No, I won't use this to sneak into any Jedi or Sith temples. It's more to keep in cover, and stay in the shadows, as interacting with beings would render the effect useless.