I respect your downvote, though the angle you're coming at seems to imply that you're soloing a champ, which is not exactly what this build is geared for. As for the Codex, it can then be replaced with Morello's for sure, as we're looking for the slight boost in AP, but more importantly, the regen and CDR.

The item progression is based on each component's cost. The meijai's at the beginning is meant to compensate for that. By the 20-ish minute mark, you can see upwards of 230 AP, if you get some kills or assists. Going for the Rod early will provide more survivability, but it costs more to purchase, and doesn't give the same damage payoff as the void staff. My playstyle is based on pure damage. Your survivability is your team.

The build also has skill in mind. I find that the stun is actually rather effective when running. 2 seconds is plenty of a gap. Also, keeping in mind that you should never run into battle unless the situation calls for it as any squishy caster really.

There will probably be tweaks to this build as I go, but so far it's been doing quite well. Thanks for your feedback regardless.

You seem to be lacking a 6th item, unless that Codex is it (which it shouldn't be). I could see it becoming a Deathfire Grasp, in which case there should be a Kage's Lucky Pick in the build, and before the Fiendish Codex. Or a Morello's Evil Tome, which is also a decent choice.

Also, Rod of Ages should be built considerably sooner, given its passive. It is not an endgame item by any stretch. At latest, it should be built before the Rabadon's, if not at least a Catalyst before Mejai's.

Aside from the missing 6th (or whatever place) item, and poor build order, this build would do okay in low elo and matches when you aren't playing against a competent team. Unless you're leaving room for wards in your inventory? A worthy pursuit, to be sure, but better left to other characters.

However, in any game with actually competent opponents, you're going to squish, and squish hard, especially if you don't work on that Rod of Ages sooner. Almost to a level of a Twisted Fate with no health items. Or a Master Yi attempting to team fight against a hard CC team. Not a pretty sight, sir.

In closing, this build needs more survivability, and sooner than you pretend to provide it with that minimal health buffer called Rod of Ages. One, single target, conditional skill-shot does not effective survival mechanism make.

I'm downvoting this, but I hope you fully understand why.