The reason why neither Li Yunmu nor the system could refuse this object was because it was the core component of Azure Dragon Deity Suit - Azure Dragon Pearl.
Among the five components of the battle suit, it was the most important one. If Azure Dragon Gauntlets formed the armor for the arm, then Azure Dragon Pearl was the source of the killing energy supplied by the Azure Dragon Battle Suit.
It was extremely important!
Battle Sage Vega's move was too ruthless.
Li Yunmu simply couldn't refuse and agreed without hesitation. Who would've known that Azure Dragon Pearl was actually in the hands of Battle Sage Vega.
Based on what she did with it, she clearly knew that Li Yunmu had obtained the Azure Dragon Gauntlets.
Thus, he didn't say anything unnecessary and agreed right away. Her two tasks went along with his current aims, and he would also obtain a component of the supreme battle suit if he did as she told, so why should he hesitate?