I Became An Immortal On Mortal Realm

Reincarnated as the son of the Duke in the Qi Dynasty, Fang Wang’s mind housed a Heavenly Palace, where his consciousness could enter to cultivate. He could practice any cultivation technique or secret art to great perfection, only emerging when it was truly perfect. No matter how long he spent in the Heavenly Palace, in reality, it was but a moment’s time. — Description from novelcodex.org