The tentacle they severed previously was not from the true form of Demon Prince Demogorgon, but rather one of his demonic incarnations.
The reason is simple: the Demon Prince is reputed to be the most formidable existence in the Bottomless Abyss, overpowering Prince Grazte of Ubar, forcing him to ally with Undead Lord Okas to contend against him.
Previously, Prince Grazte with just one hand could suppress the true form of the Father of Combat, Uthgar, making him unable to lift his head.
If the true form of Demon Prince Demogorgon had really attacked them earlier, they wouldn't have severed his tentacle; instead, he would have crushed them with just one.
Therefore, it's reasonable that Demon Prince Demogorgon didn't immediately pursue the Six-armed Snake Demon.
At this, Gaven was only disappointed, not surprised, and said to the Six-armed Snake Demon, "I need to extract the essence of Demogorgon from you for other uses."
