Do Gong's in Trouble

Do Gong's in Trouble is a Mu Lung + Nihal Desert quest started by Master Goblin.

Part of Weakening King Sage Cat: see every quest in order.

Requirements

Offer: I have no intention of being angry at Do Gong. I, the King Sage Cat, am forgiving and generous, and I can't let petty quarrel stand in our way of peaceful harmony, right? I may have been ridiculed by Do Gong, but I do not wish to fight him. I only wish to kiss and make up. Of course, you the traveler will help fascilitate this, right?
In progress: You haven't gone to Do Gong yet? I want to be on friendly terms with Do Gong ASAP! Ho ho ho!
Hmmm... it doesn't seem like the power of Master Goblin has been decreasing or anything, but...
Whaaaaat?? You lost the red marble? That precious marble...! How... how did you??? Hmmph, I can't lose dignity over this. Okay, I will forgive you for now. I will give you the red marble one more time, so... PLEASE! PLEASE give that to Do Gong.
Completion: You're back... now, if you did what you needed to do, then it'll greatly decrease the powers of Master Goblin... hmmm, what's that you're holding there?
...Huk!!! That.. That's poison?!! A poison made out of magic?