Immortal forging with a tiresome face.
Immortal forging (xiu xian) originated from a classic Daoist practice. Daoists believed that through a specific way of life that was devoid of all human pleasure, with the help of alchemy products, they could eventually evolve to an Immortal, gaining magical ability and everlasting life.
On modern Chinese internet, Immortal forging themed novels are still very popular. They introduced this mystical practice (albeit heavily modified) to all their readers, and inspired tons of byproducts, which includes a series of fan made Immortal forging themed DOTA maps. Many people are staying up late in the night, or even staying up the whole night, just to play these maps through. The term Immortal forging is consequently used as a humorous synonym of "staying up in the night."
Those DOTA maps are not as popular as before, but the term stayed strong.