When the Jedi of 3990+/- BBY were being hunted and the sith formed some sort of tether in the force which would allow the sith to follow the Jedi anywhere they and went. The further the Jedi would run they were hunter and they would grow weary and eventually succumb to the dread that crawled in their skin and they would be driven mad with thoughts and premonitions of their own death. This is is light years worse than what Malgus and Vader did to the Jedi of their day at least they could run and not hunter like dogs. Malgus and Vader weren't strong enough to form tethers and plus the rule of two didn't help either. All the inquisitors of the empire had to use was word of tongue to find Jedi and even then KANAN a mere apprentice killed the Grand Inquisitor with relative ease, and the rest were man handled by a damn near 60-70 year old Maul who was also a sith assassin. Although the sith of Malgus' say were far better in number and skill they were still fairly evenly matched. What they Jedi had to go through during the Sith Triumvirate's day is torturous and vile. And that is precisely why I LOVE the sith of old for what they could do to the mind and the soul of those they sought out not just give the ptsd give them eternal dread.