The target is surrounded by a dark mist and has his goals and ideals rewritten. The spell can be broken by putting some sense on the victim's head or even by simply asking what they are doing that which usually makes them unable to answer correctly.
Depending on who and when the spell is used, the results can be totally different. It seems to be incomplete according to Giblet, who stated that even with the perfected version, he is far away from reaching the Super Saiyan God form.
Usage and Power
It was initially used on Raditz, who, instead of being a prideful Saiyan, he just wanted to destroy everyone on his way, especially Vegeta and Nappa, after realizing Shallot was trained by them. Despite his Ki "skyrocketing", he was unable to defeat Gohan (from before his battle against Vegeta and Nappa), Shallot and Zahha combined power.
Turles was the next one who displayed that form, instead of searching for power and govern the universe, he simply started dozens of senseless conflict, changing his side constantly, only to generate even more battles. When asked by Shallot why he was doing such things, he was unable to say why and was ultimately defeated by Shallot's newfound power.
Dr. Gero and all his remote-controlled clones were brainwashed, making them believe that people only would respect his science if he creates the Ultimate Warrior. Even when the original Dr. Gero was killed, his Clones were still brainwashed, however, the spell was broken when Android 16 made him remember his original goal.
In the middle of the Super Cell Games, Ribrianne was revealed to being brainwashed. She became even more "extremist" about love, saying, and doing things that even Kakunsa and Roasie were unable to agree. She was released from the spell when Shallot made her realize that she was hurting her friends.
Kale was brainwashed in front of Shallot and Caulifla by Babidi, the spell was slightly different this time, instead of changing Kale ideals and goals, he just took advantage from Kale weak heart, making her believe that Shallot and Caulifla were a couple. She was ultimately freed thanks to Caulifla and Shallot.
When Babidi menaced to destroy every single human on the Earth, uncountable combatants and Saibamen were brainwashed to help him on such thing, however, it is more like they just are on a mindless state and not with his ideals and goals rewritten. Bojack was brainwashed on that conflict as well, his arrogance and sadism skyrocketed alongside his Ki, making him call himself as "The King of Universe", but he was ultimately defeated by Adult Gohan, Cabba and a still-young Future Trunks.
After Beerus realized that Babidi wasn't the mastermind behind this whole tournament, he asked why Babidi was gathering so much energy, a question which he was unable to answer. He doesn't seem to be powered up by such technique but only had his memories hugely rewritten.
Giblet was revealed to be powered-up by the technique, and even is an ally of the mastermind, demonstrating an improved version of the technique, being able to rival with Super Saiyan 3 Shallot, however, he was no match for Super Saiyan God Goku.
When Shallot, Bulma, and Jaco returned to Earth, they found Nail fighting a powered up Lord Slug. While Shallot stated that he didn't even need to turn into Super Saiyan to defeat Slug, he noted that he was constantly getting stronger instead of just receiving a single boost on his power. Instead of being brainwashed, memories of every single battle that Shallot had were implanted on his mind.
Later in the game, Shallot fights against Majin Vegeta, who was being powered-up by the Improved Version of the technique displayed by Giblet, while he was initially able to overpower Super Saiyan 2 Shallot, he was no match for Super Saiyan 3 Shallot. Likely Giblet and Super Buu, Vegeta wasn't brainwashed by the technique, but instead is simply being powered-up by it, since he is an actual ally of the Mastermind.
A Frost from before the events of the Tournament of Destroyers was powered-up by the perfected version of the Dark Ki, but his case was the same as Lord Slug, instead of being brainwashed, he now knows everything about Shallot and every battle he had.
The technique was proved to be able to brainwash even likes of Android 13, an Artificial Being. Despite being an ally of Mastermind, he was brainwashed instead of just being powered-up like Zamasu, Vegeta, and Super Buu. Android 15 noted that he totally forget about their original goal of destroying every Goku from the history, and instead was simply trying to kill Shallot, which was just a sub-note on their original goal.