The Tubians were once a magically advanced society until the MI rained from the skies and attacked with violent force.

The MI nearly wiped out almost all the Tubians using their technology. The Tubians tried using spells to discourage the MI attacks but the MI kept coming. 

Some sketchy scientist decided to take MI and Tubian DNA to make a new being called the Tubmi.

The Tubmi became infectious and turned all the MI into Tubmis. With their tubian dna, they were able to bypass the tubian spells, thus they killed all the Tubians.