Dabi originally applies to be a member of the League Of Villains after hearing about the incident of the Hero Killer Stain revealing his mission to cleanse society of fake heroes via the local news reports. After Stain is captured by the authorities, Dabi and another Stain enthusiast, Himiko Toga, meet up with Shigaraki Tomura and Black Mist in their bar and headquarters. Their first meeting ends up being tense, since Tomura found Dabi's personality to be quite rude and the latter's idolization of Stain further annoyed the former. This leads to a brief scuffle that was soon stopped by Black Mist. Black Mist then tells Tomura that they could use Dabi and the other villains who wanted to join as potential allies which leads to the recruitment of Dabi and the other villains who wanted to join the League Of Villains.
Dabi is later seen with the Vanguard Action Squad, a group composed of the new members of the League of Villains, preparing an attempt to kidnap Katsuki Bakugou at U.A. High School's forest campsite when the hero classes were training there. He sets up a forest fire during the mission, which draws out Eraserhead . Dabi then attempts to ambush Eraserhead with a point blank fire blast but Eraserhead dodges and immediately incapacitates Dabi after turning off his quirk. Eraserhead attempts to interrogate Dabi about the League Of Villains whereabouts but is distracted by some of his students appearing. This allows Dabi to regain his quirk and escape. While melting right in front of Eraserhead, Dabi mocks the security measures taken by U.A.
Dabi primarily displays an aloof, indifferent disposition to most scenarios. He is confident in his abilities, sarcastic and rude to his foes and allies alike. Underneath this calm exterior Dabi is actually quite passionate under the right circumstances and can be seen with a large maniacal grin on his face.
Dabi's quirk allows him to emit massive amounts of blue flames from his body which he primarily uses in combat to overwhelm his foes with the sheer power of his flames