Jacen had been busy. The moment he had felt that sharp spark that was the Force equivalent of a hurricane, he had known it was Anakin. More than likely, Anakin turning into Darth Vader. He had grabbed his lightsaber, and had been going through his "kit" of items for use in more unconventional combat. His skirmish with Jaina over Anakin had been a useful lesson in the value of non-standard tactics in combat, and he expected that it would lend him an edge against Vader. Supposing, of course, that that was much of an edge in the first place. Vader was strong, probably stronger than he was. Didn't mean he wouldn't put him out of his misery.
He didn't bother to open the door when Tenel Ka knocked. "Come in," he said, as he continued to inspect his kit.