Approximately, the Demon Sect's original plan was to sharpen the blade on the battlefield itself, using war as tribulation training. They meant to take this bunch of newbies and charge straight into the Kunlun Secret Realm, killing all the way through—meeting tribulation, crossing tribulation, encountering demons, slaying demons—breaking through one pass after another, tempering them at every step. On one hand they'd rely on the many layers and unfathomable dangers of the Kunlun Immortal Mountain secret realm to conceal their tracks; on the other hand they'd use slaughter and tribulation as training, speed-levelling a batch of experts, and finally rendezvous with the main force at Heavenly Mountain to fight a decisive battle against our Divine Sect.
