(Not a mindless power fantasy, but an unstoppable harem romance with an emphasis on worldbuilding and filling in the gaps in the original.)
He was once the Profound Demon Emperor of the Heart Demon Clan, with a cultivation level three major realms above that of a Dou Emperor. He was preparing to enter seclusion and break through to the Heavenly Demon Emperor realm. However, the higher-ups of the Extraterritorial Evil Clan had imposed layer upon layer of restrictions on advancement, so he had no choice but to seek another path. He tried to travel to other times and spaces to accumulate power, but accidentally transmigrated to a mortal planet called Blue Star.
There, he discovered Blue Star's online novels... the Battle Through the Heavens trilogy.
