Mayfly (Rap, Dance, Vocal Units) is a brief collaboration between 3 groups for the show ''<Kingdom: Legendary War>'' consisting of BTOB, Stray Kids, and ATEEZ. '''Creation:''' As ATEEZ had taken first place in the preliminary voting for Round 2 (Re-Born challenge), they were given the opportunity to choose their collaborating groups for the first part of Round 3 (NO LIMIT). Via majority vote, they chose to group with BTOB and Stray Kids. They chose the name 'Mayfly' after the insect that only lives for one day as this was a collaboration that was brief and fleeting. The overall, general leader was the youngest member of the collaboration, I.N, while the 3 participating members of BTOB were the leaders of their individual units. (Note: Changsub was not a part of this collaboration, as he had become ill during the Re-Born episode and was resting and recovering during this segment.)