Mortals Start Cultivating Immortality but Are Sold to Mine and Become Invincible

I thought I could reach heaven in one step by joining the Immortal Sect, but my qualifications were so poor that I became a slave in the mines. My fellow brothers and sisters have been building foundations and elixirs one after another, but I have been silently mining in the dark mines for three hundred years. Until that day, I dug through the ancient forbidden land, and the mountains of immortal weapons and elixirs inside were actually just burial objects...