Honkai: Star Rail has introduced players to Dr. Ratio, releasing a trailer that shows the character in action against various enemies. For the very first time, Honkai: Star Rail will give players a free five-star unit, Dr. Ratio, who will be available to claim until the end of patch 2.1. Once the second part of 1.6 is released on January 17, he will get his own banner like every new character in the game.