Dragon Ball Super is a series that has taken the power of Saiyans to levels few fans every expected. Goku and Vegeta went from Super Saiyans to Super Saiyan Gods, then combined God and Super to form Super Saiyan Blue. Both Goku and Vegeta than surpassed that, to achieve truly god-like power in the forms of Ultra Instinct (Goku) and Super Saiyan God SS Evolved (Vegeta). However, neither Goku nor Vegeta truly mastered their latest transformations, but the current Dragon Ball Super manga arc has forced Goku to step up his game, and now we know just what his Ultra Instinct Sign form is all about!
Dragon Ball Super manga chapter 59 SPOILERS Follow!
In the Dragon Ball Super's latest "Galactic Patrol Prisoner" arc, ancient evil sorcerer Moro has come to Earth with one goal: suck the planet dry of all living energy - particularly the massive powers of Goku and Vegeta. Goku and Vegeta split up to train and unlock new powers that can defeat Moro - after nearly being annihilated by the villain. For Goku, his training with the angel / Galactic Patrolman Merus let him better understand and master Ultra Instinct - in both of its forms.
During the Tournament of Power, Goku first manifested Ultra Instinct in its lesser form, Ultra Instinct Sign. It took him a few times of trial and error combat before he finally exploded into his full Ultra Instinct form, to battle Jiren. However, after training with Merus Goku is able to manifest Ultra Instinct Sign at will during his battle with Moro. That allows him to move at ridiculous speed and counter Moro's energy absorption powers. However, Goku's new power is not quite as invincible as it initially seems.
In a cut scene from Moro and Goku's battle, we see angels Whis and Merus observing the fight. Whis is impressed that Goku has mastered Ultra Instinct - but Merus has a confession to make: he didn't quite get the job done as Goku's instructor. Goku only mastered activating Ultra Instinct Sign - he never achieved "the true Ultra Instinct form."
Once Moro recognizes the nature of Goku's power (and its limits), the villain is able to counter it quickly. As Whis explains, with this form of Ultra Instinct, "Sign serves as the gateway to Ultra Instinct, but it isn't stable. Maintaining that instability consumes an enormous amount of stamina."
This explanation of Ultra Instinct Sign only makes the power more confusing. Ultra Instinct is supposed to be about achieving a complete level of tranquility in the heat of battle, but apparently working up to true tranquility consumes a ton of power. Yet, when Goku did achieve true Ultra Instinct in the Tournament of Power, that form still almost tore his body apart. Tranquility: not for amateurs, according to Dragon Ball Super.