"Surprise Lord White Avian would give him the treasures". Clearly it is either the author forgot or something but keeping the treasures have strong karma problems.
Karma problems come from receiving favors. He's going to need to repay White Avian in the future. That said, saving White Avian's life should be enough to repay any karmic debts, and we already know Meng Chuan's going to do that once he learns about it and has the power to do so.