As for the Nightmare Dragon, it was still unknown.
However, based on the previous breathing techniques that had been fused, it probably still hadn't broken out of the bounds of legend.
Therefore, if possible, the next step would be to evolve the Sky Dragon, Scarlet Dragon, and Nightmare Dragon again, striving to reach the Mythical level, and even beyond to the Super Mythical level.
Eventually, these Super Mythical level breathing techniques would be fused together.
Then the ultimate biological breathing technique that Levi once conceived should take shape.
When that realm was reached, wouldn't he be able to move unchallenged across the Multidimensional Plane?
Even the gods of the astral world would have to lower their heads in his presence.
In addition,
Levi found that his breathing techniques were also involved in many worlds.