Shu Xiaolou was clearly showing interest in Lin Jin's astonishing needle manipulation skills. However, he was also aware that to ask for it directly would come across as greedy and inappropriate. Hence, he offered one of his spells in exchange for Lin Jin's information.
Lin Jin was intrigued as well.
Indeed, the pulse-seeking technique was an incredible needle manipulation technique. Though, since Mr. Shu was a Rank 5 appraiser, Lin Jin figured that his spell would be just as extraordinary.
Coincidentally, Lin Jin did not know many spells. The Spirit Energy Finger was one, and then there was Fire Spirit Possession and Spell Negation, both of which needed his blood contract to be utilized.
He also knew Carrier Cloud, Camouflage, the Five Elemental Edict Amulets, and Dragonfire which he created on his own.
