Because Old Gu had his memory severed, his understanding of the Forbidden Land was also nil, only having heard about it.
In the Immortal Realm, the Forbidden Land was also a place that made people tremble with fear.
It was too dangerous there, even an Immortal Venerable might be buried there, yet it was also filled with opportunities. It is said that there are Great Medicines that allow one to live a second life without reincarnation marks, divine objects that directly extend lifespan, and more commonly, the corpses of those almighty who entered seeking fortune.
Acquiring it might contain the entire Cultivation Fruit of an almighty being, naturally making it precious.
Old Gu didn't enter the Forbidden Land because his lifespan was running out, but because he was unbelievably bold and adventurous.
However, his luck was truly against the heavens; not only did he come out alive, but he also had a true encounter.