He knew Xu Qing as she is from the same Mountain as him and was, obviously, suspicious of her identity to be able to become a personal disciple of Ksitigarbha, the Lord of the Fourth Mountain and Sea.
Lin Cong first met Meng Hao in the Windswept Realm. He attacked Meng Hao in the location of the Eight Mountain after Meng Hao took it over from Han Qinglei. He believed Meng Hao to be much weaker than himself, and, thus, was supremely confident. However, he was defeated by Meng Hao without even using any of his cultivation. All Meng Hao used were the Seven God Steps he got from Su Yan, and the three punches he learnt in the Ninth Golden Stele of the Nine Seas God World (i.e Life-Extermination Fist, Bedevilment Fist, and God-Slaying Fist). This thoroughly flabbergasted every single member of the Echelon who were watching the fight.
Meng Hao then chased Lin Cong all the way to the Fourth Mountain, and even managed to kill him once because he had threatened Xu Qing.
After the Imperial Emperor of the Windswept Realm unleashed the Traitorous Sutra of the Rebel Dao, Lin Cong, Han Qinglei, Dao Heaven, Yuwen Jian, and the other members of the Echelon were chained to it and their life force was being absorbed. Meng Hao saved them, ending all enmity between them.
After leaving the Windswept Realm, Meng Hao gave Lin Cong a Cosmetic Cultivation Pill to give to Xu Qing.