@Ashurek, Infinity Edge is a great item with him for crits and Atma's is in the optional items.

Infinity Edge? Fast Wagmog without atma?

No way

Just Ignore TheAvant, this is like the 6th guide I've seen him downvote. He's a troll, and most likely bad at LoL.

HA You make me laugh, My build I above yours and im not scared of your ****ty one, one thing I know you do. You voted me down which resulted me what "The great PRO" make....I got this ****.
I don't like it or you, I voted down problem?

I know, but I didn't really deserve it at the start haha.

I already gave you a +1 haha, but yea.

Thank you, worthy of your +1 now?

Well, as I said. Atma's Impaler is cost effective. it's not the greatest item, but it gives you a bigger bang for your buck, somewhat. That's why i prefer it. As for Clarity, Darius has rather low mana costs on all of his moves, and he does quite a lot of damage with all of them. You shouldn't need to spam to really hurt someone. And, it's silly to build extra armor pen for one tank. Especially when if he's really a problem you can just take half his health out with Noxian Guillotine. But yea, good changes!

I don't really like Atma's Impaler for the same reason as I commented on your guide, the slot could be better used elsewhere, but I might add it to the viable item list due to many people having asked for it. Maw of Malmortius is in my AP Based Team build because of having those strong ultimates like Karthus's but it may be added to the AD Based Team because of the extra attack damage because of health being missing. That's what I think, if you're spamming skills so hard that you need Clarity, you're playing him so wrong it's not funny. And if you're spamming that hard, you should be getting Blue Buff if your midding AP Caster doesn't need it because getting Clarity when you could be getting Ignite or Exhaust to shut down the opposite team, is just a waste of a summoner spell. As for the Greater Mark of Desolation, I still like to have that little bit more ArP for getting rid of any armour your enemy decides to build, but I may also add Greater Mark of Attack Damage for AD Heavy Team Runes as a choice for the player.

Well your base guide looks fine to me, except it lacks some defenses. It's a lot of health, and only a tiny bit of added armor. That's why I prefer the Atma's Impaler and Maw of Malmortius. Also, I'd remove Clarity from viable summoner spells, let's face it, if you're spamming that hard, you probably doing it wrong. And lastly, Darius doesn't need Greater marks of desolation due to Apprehend.

Also, @OTGBionicArm, anything for me to improve upon?