Such powerful spirit sense was clearly immortal king spirit sense but this immortal king wasn't He Yi immortal king, it was Chang Xin immortal king. He was immortal king peak stage and one of the top immortal king of Yuan Le heaven. He's also the master of Guan Feijian.
The reason he took a heaven immortal disciple was purely due to Guan Feijian's potential. Plus, Guan Feijian gave him the jade slip for Hao Heaven finger, he really liked this disciple and felt Guan Feijian's future would be no lower than him.
He thought that on the mere dao seeking tournament, no one would be able to threaten Guan Feijian so he didn't care about it at all.
What he didn't expect was that when he came to the city, he got news of his disciple dying, he was killed on stage by his opponent. He didn't believe it at all at first but when he heard it was an abstruse immortal middle stage knowing a sliver of space law, he believed it.
