The Emperor had heard of the shrine on the territory, had been briefly interested by it, checked it out, and decided it was not worth his time.
He, however, did feel it was a threat. With the Force stronger there, it could pose a threat to himself.
And by the possibility, it meant the presence of the dead.
When the Emperor investigated the temple, he had ruthlessly destroyed the trial and been greeted by not only Yoda, but the spirits of the Jedi Guardians. And when they appeared, the Emperor had to fight his way out, and left.
But he had to keep his eyes on the true goal- Vader, and the possible replacement. He knew Vader was liable to turn on him and he knew what lengths Vader would go to for his children. He had to change his plans, again.
So, the Emperor had focused his targets on Almir. He showed the most promise.
But it would be slow, but the fruits from Patience's tree were always the sweetest. So, he would wait.
The Emperor moved to the center of camp, and rose his voice. "Meet and greet!"