AP Leona mid may sound odd, but in practice it works quite well. She does tons of burst damage with her full combo, and has tons of cc. Her kit makes her such a good mid laner that is strong in both late and early.

Leona relies very much on her items, as they are the source of her damage and overall presence in the game. Items giving both AP and health can be very useful, to give her the health sustain required to jump into fights, dealing tons of burst damage received through items such as DFG, lich bane and rabadons, deal massive crowd control to the enemy team. and survive it all with zhonyas and rylais.

Leona's kit is strong in mid, but you have to know how to use each ability. Her W deals a great deal of damage and gives her a decent amount of armor and magic resistance, and can be used effectively to clear waves, or deal AoE damage in a teamfight. Her Q unleashes quite a bit of damage with lich bane, and can be used to harass or last hit minions. Her E is simply a utility move, to engage or to clear a wave. Her ult is used to CC and deal AoE damage. In lane it can be used with your E to engage or to prevent escape.

Ignite and flash are the best possible spells on Leona mid, ignite used or course to finish, because she lacks any ranged abilities to do so besides E, which may send you accidentally flying into tower range. Flash, as per usual, is used to escape because Leona has no abilities to escape, besides stunning an enemy repeatedly.

Leona mid is often considered troll, and your team mates may become angry a you for playing this in ranked, or report you. This build is simply for fun, but if you find it works in ranked, have fun.

Leona team fighting is very strong, as she can deal tons of AoE damage and CC, as well as single target.

AP Leona mid is very out-of-meta and troll but it can be very enjoyable and in normal queue, who cares what you do! When played right, Leona mid is a fun thing I tried, and I hope everyone enjoys this build, so good luck and have fun.