MTL - Chronicles of Primordial Wars - Chapter 4 The child coming out of the hole is terrible.

A skilled but unfortunate modern-day assassin was killed in a freak accident. However, he soon found himself summoned to another world by an evil wizard, who had him possess the body of a boy as an experiment. After successfully planning the evil wizard’s downfall, he used the wizard’s body as a springboard to gain influence and power in his new world.

- Description from Novelupdates

Twelve zodiac animals represented the months of the Lunar calendar. No one was aware,however, that these twelve representations were Guardian Gods. These twelve positions were passed down the twelve patron bloodlines. They possessed the ability of the zodiac guardians and silently protected the East.

In the East, the auspicious Qilin, possessing royal blood, descended, reigning over the Twelve Zodiac Guardian Gods, who devote all of their power into protecting the East.

A ruffian Qilin, an Earth that transcends all expectations, a legendary city, and the patronage of the Zodiac animals together create an unforgettable novel.

(Rat, Ox, Tiger, Rabbit, Dragon, Snake, Horse, Ram/Goat, Monkey, Rooster, Dog, Pig)

- Description from Novelupdates

After transcending to a new world, Ye Xuan miraculously obtained the Swallowing System.

Not only could it swallow everything (wink wink nudge nudge), it could also extract bloodlines, martial arts, godly weapons, medicinal pills, treasures…

“This (beer) is way too strong! Don’t challenge me! Do you believe that I can’t swallow your divine swords?”

- Description from Novelupdates

He became a teacher at the best magic academy in the empire.
….For being mistaken for someone else.