After I Transmigrated into a Book, I Stole the Protagonist's SSS-Rank Black Dragon from the Start

Chen Mo transmigrated into a book and became a disposable villain in the novel Lord of Ten Thousand Beasts. He was a mere plot device who awakened an S-rank Shadow Demon Tiger, only to be killed in gruesome fashion by the protagonist, who had awakened an F-rank Stone Monkey. At first, all Chen Mo wanted was to keep his head down and stay alive. But the moment his System activated, he smiled. 【Ding! Spend 100 Authority Points to evolve the D-rank skill Bite into the C-rank skill Tiger King's Bite!】 【Ding! Spend 5,000 Authority Points to evolve the SS-rank Shadow Demon Tiger into the SSS-rank Shadow Tiger King!】 【Ding! Spend 100,000 Authority Points to evolve the Epic-rank Obsidian Dragon into the Legendary-rank Dark Demon Dragon!】 … With the System's help, Chen Mo not only trounced the protagonist, Lu Chen, at every turn, but also snatched away all his opportunities. While Lu Chen was still congratulating himself on getting an SSS-rank spirit beast, Chen Mo had quietly gathered the Four Divine Beasts, including the Black Tortoise. The original protagonist? Sorry, I'm the protagonist now.