At Lu Ming's current level, he could manually upgrade to level 16 anytime he wanted and head straight to the second floor of the Nether Ghost Tower.

However, before that, he needed to ensure that Lin Youwei also reached level 16 to meet the entry requirements for the second dimension.

Grinding the Nether Ghost Tower was primarily for farming Soul Stones to make money.

If the primary goal shifted from making money to leveling up, then clearly the Nether Ghost Tower was no longer the most suitable place to conquer.