I had to research this, having little knowledge of the Twilight Forest mod, so please say what you think, and suggest new ideas.

The Minotaurs

Once, long ago, in a world trapped in eternal twilight, a dark wizard began to experiment on creatures from the Overworld. Players were transformed into Redcap Goblins, spiders into Hedge and Swarm spiders, and squids into Wraiths. The wizard did this, by trapping the mobs in an area, which they would have to adapt to survive in.

As time went one, the wizard had less mobs to experiment on. So he started taking good mobs, like pigs, to experiment on, but they just turned into boars, which was a boar. So, the wizard took cows next, trapping them in a Labyrinth.

As time went on, the cows started to evolve, as the wizard had planned. To get to food quicker, they started to run faster, which coupled with the growth of horns meant they could ram live prey. To eat the food better the cows started to stand on their hind legs, leaving their hands free. They also lost the fur on most of their body, as down in the hot tunnels, it was not necessary. And finally, they made tools out of what they had to build with. Mainly gold.

Usually, the wizard released the mobs after they had evolved to his liking, but before he could release the cows, now Minotaurs, but before he could he died of old age. He had cast spells to keep him alive, but all they did was keep his sprit on the earth, in his tower still protected by his creations, while the Minotaurs stayed in the Labyrinth, waiting for their next meal.