The ability of force sight allowed Krayzen to see through every floor, every door, etc relative to his own position. It was like having a map of the interior design of the tower, which benefited Krayzen. That combined with his sensory boost due to his natural abilities, and the dark side nexus notified the One Sith General that [member="Aela Talith"], and the Chiss Padawan were at the location where the artifact was; furthermore, he determined in a fraction of a second that they probably had the artifact by now. After all, they had been in that position for it to be enough time for them to get the artifact.
As he had entered deep into the tower, Krayzen determined that it was better to leave. Aela and the Chiss were -somewhat- far away from him, so he wouldn't get attacked; they weren't any traps set up , and no device that would connect a trap to someone's device(therefore making it a slave rig system).
Due to the exit point being big( the one that was behind [member="Jacen Voidstalker"]), Krayzen would easily fit, and had a lot of room around him to counter attacks. As he run to Jacen, he threw his
GS Grenade at the man as he was using his Grav Glove, Krayzen being able to see what was behind him(since he has 360 degree vision, and therefore could see if Aela and the Chiss if they were close to his distance). There were no traps, or anything wrong with the strucutural intergrity of what was around him so Krayzen wasn't going to get hurt; furthermore, there were no Jedi close to Jacen(NPCs is what I'm talking about) so Krayzen wouldn't get pincered, although he still maintained his senses.
As soon as the GS Grenade got 2 meters from Jacen, white phosphorus would be emitted; furthermore, a sonic/concussion blast combination would be sent toward the powerful Jedi Master who had no armor on him(basing it on the character profile, and the fact that no gear was listed in your posts here). One had to consider the fact that Krayzen did not have any weight on him since his muscle suit took all the weight off him; furthermore, Krayzen had 3x the athletic abilities of a human, meaning he had 3x better strength, and therefore better throwing power, so the grenade would travel pretty fast.
While he did this, the man let out a burst of force lightning, aimed at the Jedi Master's center of midline in his back. The attack was at the center(vertically), and horizontally, meaning that if Jacen moved to the left, or the right, their was still a high chance of the attack striking the veteran Jedi.
Due to the grenade being smart-linked, and having been activated while it was still in the air, Krayzen wouldn't be distracted by the attack. His lightsaber already activated, the One Sith General maintained his defenses, ready to fight any Jedi that attacked/defend himself. The Sith was ready to strike, his lightsaber ready as he wished to defend himself.