"I never expected that just reaching the fifth realm would grant immortality... If it weren't for the fact that one's realm could decline, training up to the fifth realm might actually be quite enough. Survive for a few thousand years in the real world and with the speed of technological development, who knows, you might even survive until brain-computer interfaces exist, enabling mechanical ascension."
Unfortunately, this so-called immortality is ultimately illusory; without Spiritual Energy, the realm will inevitably decline, reverting one back to a mortal.
It seems that in the way of immortal cultivation, if you don't advance, you retreat.
The Sixth Layer, Tiger Body Dragon Shape, I have no idea what effect that has... It does sound pretty cool though.
"Senior, have you managed to master Tiger Body Dragon Shape?"