As his name implies, Kurogiri's entire body is made out of mist. He normally wears a very elegant suit with a tie and has five metal plates that go from around his collarbone to just below his eyes.
In his villain costume, he doesn't wear anything and only has three metal plates around his neck.
Kurogiri has a level-headed personality, which often serves to ground Tomura Shigaraki's immaturity. He is intensely loyal to both All For One and Tomura. He is very polite and well-spoken, even to enemies, which is shown when he greets the students and introduces himself in a formal manner. However, like his fellow villains, he also has shown a sinister side by telling the students that they would be tortured and killed when warping them to various areas of the U.S.J. He is very cooperative, reasonable and reassuring to his allies as he told the League of Villains' recruits to patiently wait for Tomura's answer.
Warp Gate: Kurogiri's Quirk can create and manipulate a dark fog that acts as a portal. Whenever he produces a mass of the dark fog, it transports anything it comes in contact with to a location of Kurogiri's choosing. His Quirk is coordinate-based, so in order use it, he needs to know the exact location.
He can also create multiple exit points where the things that touch his fog will emerge, as shown when he stops the fight between Tomura, Dabi and Himiko Toga and each of their hands appear in a different location. This Quirk's usefulness and rarity makes Kurogiri an extremely vital asset to the League of Villains, as even Tomura, despite being angered with Kurogiri during the raid on U.A. High, did not dare punish him.