My Dao Companion is a Mini Demon Lord

【An ancient man calmly time-travels as the bottom VS A demon lord who can grow or shrink as the top】 Su Qingyun was gathering herbs on a mountain when he accidentally fell off a cliff. Believing he was doomed to die, he unexpectedly found himself transported to another world. Good news: there are cultivators here. Bad news: they are all demon cultivators. Su Qingyun stumbled into a cave and discovered a man sealed within ice crystals, with a strangely shaped ancient sword stuck through the top. He approached out of curiosity, and the man inside the ice actually spoke. The man: Young one, this lord sees that you are fated to meet me. Would you be willing to cultivate immortality with me...