Chapter 34: 34reincarnated as superboy(young justice(dc)) with shiro's(fate) powers
Mc will be a reincarnator(mostly because i dislike superboy's and archer's personalitys and shiro would have been too weak), probably without foreknowlage of young justice but they MAY have SOME knowlage of dc
The in-universe explanation for superboy to have magic would be that the light(the supervilan group from young justice) would have known that superman had no protection against magical atacks, and so they hunted down for magic to add to their new weapon(superboy) and got their hands on a certain single use magical ritual that came from another universe: the servant summoning ritual. They altered the ritual so the servant won't have a phisical body, instead they made it so the summoned spirit would inhabit superboy's body(this beeing done when the clone was still a young enought fetus so that it haden't grew a soul yet). The light decided on giving superboy this type of acess to magic instead of any other because of the comand seals that would come with the ritual would enforce the light's control on the new weapon. When superboy got released from his pod by robin, aqualad and kidflash, he was ordered by desdemond over a comand seal to capture the 3 boys in front of him, mc just traced a [rule breaker](medea's noble phantasm that alows her to cancel magic contracts) and stabed himself with it, freeing himself from the master-servant contract he was in with desdemond. Now normaly servants need a master's mana to survive, but because archer was bound to superboy's phisical body he can just feed of what his body produces, making mc his own master and servant