Mo Jingyan had already taught Great Grandpa how to use the contract to bind the Jade Pendant. If he had no issues, wasn't killed, and didn't revoke the contract, the other party couldn't force him to surrender this Magical Treasure.
After he contracted it, the Magical Treasure automatically became invisible.
He also taught him how to cancel the contract. This kind of contract can also be used on Storage Bags.
Grandpa also contracted the Storage Bag, and it became invisible on his hand.
Then he tied the Storage Bag with a string around his neck.
This string is also from the Storage Bag. The bag is invisible, and the string is invisible too.
"Yes, Grandpa, I also want to go inside and take a look."
Mo Jingyan's father watched as everyone else had good things, while he had nothing.
Feeling envious and jealous.
Then they were all invited by Great Grandpa to enter the Jade Pendant Space to take a look.
