Hello! My name is WoLF42, the author of this guide. :)
I`ve been playing Mordekaiser for quite a long time and I think I`ve found one of the most efficient and generic build. Note that this does not substitute for every single game, but I will explain the thought process and reasoning behind my reasons.

Hope this guide helps you achieve victory as a veteran Mordekaiser or a first time Mordekaiser.

NOTE THIS IS WRITTEN FROM 1.0.0.136
I.E. Nerfs prior to this won`t be mentioned

Mordekaiser is NOT a tank. I`ve been raged at by randoms who complain that I don`t get Sunfire Cape and Force of Nature. Yes, they are good items, but they simply do not synergise as well as the other items I have placed as the recommended items. He has no peeling CC, let alone ANY CC (without Rylai`s).
TLDR; ASK THEM WHY THEY DIDN`T PLAY TANK


Mordekaiser is a PUSHER. Hopefully you can rely on your allies to defend a tower well. Split pushing is something Mordekaiser does well compared to other champions. His base attack speed is higher than most, which allows him to take down towers with ease. If there are enough champions in other lanes, you should feel free to take down a tower.
TLDR; TELL THEM THAT TOWERS > KILLS

Mordekaiser can go ANY LANE. Yes, he goes where he pleases. He is generally notorious for solo top, but he is great in solo mid since his shield can mitigate high amounts of burst damage such as LeBlanc or Ryze.

Solo bot laning
Yes he can do this. Here is my logic: a support will keep a lane warded and sustained, attempt to deny opponents by zoning/harassing and assist in grabbing kills. Mordekaiser can do most of these things. He can:

Avoid being harassed with his shield
Harass with his E ability, Siphon of Destruction
Win damage trades very easily
Make enemy supports have to use mana by making them heal/shield allies.
Sustainable damage output.
Out-sustain as he uses one resource bar (HP, and no MANA)

He works as the farming bot lane champion (normally AD, but Mordekaiser works as well or better) or as the "Support". Support players may cringe at my suggestion, but I have reasoned why he can work with anyone. His role is to harass and zone. You may say, "He`s going to run out of health". Well runes and masteries counter this.
TLDR; HE CANNOT CC/SUSTAIN ALLIES, BUT CAN DO SUSTAINED DAMAGE TO MAKE UP FOR THAT.

Pros

Moderate to strong laning phase
Can take any lane including bot (will cover this later)
Tons of damage
Always shield never die
WoTA + WoTA combo-able
High farm capabilities
Doesn`t fall off late game due to AOE
Ultimate is a 10 second slow with Rylai's
Great baiter with shield
Aggressive play is rewarding
Late game anti-carry carry

Cons

Can be harassed - moderately short range compared to casters
Relies on spellvamp/regen early game
Requires health pool earlygame
Full MR rune pages
No CC whatsoever without Rylai`s
Can be kited easily
No gap closers
No dashes/blinks
Minions have to be near champions for maximised output

Mordekaiser can shine through early game despite his high health costs to cast spells. Rune pages can offer an additional 8.1 HP/5 regeneration. This equates to 1.62 HP per second. When matched up against champions without these runes, you will have a relatively strong footing against your opponent(s).
The HP/5 Quintessences are only there if you want a safe laning phase. If you wish, you can exchange them for Flat AP/Movement Speed/Magic Pen/Magic Resist, but I find HP/5 highly sufficient.

Quintessences
3 x Greater Quintessence of Vigor - 8.1 Health Regeneration per 5

Marks
9 x Greater Mark of Insight - 8.55 Magic Penetration

Seals
9 x Greater Seal of Resilience - 12.69 Armor

Glyphs
9 x Greater Glyph of Warding - 13.41 Magic Resist

Masteries are 9/21/0
The reasons I don`t use utility is that nothing stands out there.
Why do I get 21 in defense when he`s not a tank?
He has to survive (more about THE SHIELD later on)
Why do I get 9 in offence?
Well where else to spend it?
Y U NO MOVEMENT SPEED UTILITY/DEFENCE?
Mordekaiser is a sponge. He doesn`t need to be really quick. He is more about doing damage than he is receiving damage rather than sticking to a champion. He is not an assassin.
Why did you pick "Enlightenment" and "Vigor" in utility?
I thought about getting 3 points in the armor mastery, but it really mitigates less damage than the extra damage dealt with the Cooldown Reduction, especially because every point of armor after a certain point is less effective. The HP regen mastery is just for the laning phase.
Why not the "Initiator" mastery?
I know that it is useful (there is no comaparison to movement speed but itself) but it isn`t necessary.

Items are one of the biggest things that separate guides. I will explain why I take one specific item over another.

Regrowth Pendant vs Amplifying Tome
Ahh. Many players who don`t own Mordekaiser tend to pick the Regrowth Pendant and a Health Potion. This is not a bad option. I mean, getting 3 HP per second is really quite something. The Amplifying Tome only increases the damage of the Siphon of Destruction (E) by 12 damage [0.6 x 20]. Over 4 seconds, one would argue that Regrowth is the better option. It is! For the first few minutes of the game that is. It builds into Warmog`s or FoN, both of which aren`t completely necessary unless you don`t have a tank. Amplifying Tome builds into spellvamp items, which are absolutely CORE on Mordekaiser. Also increased damage = increased shield ;)
TLDR; REGROWTH DOES NOT BUILD WELL INTO LATE GAME ITEMS. FoN/WARMOGS TOO MUCH $$$

Sorcerer`s Shoes vs Mercury Treads/Ninja Tabi
The more damage you do, the more shield you get. True, you are missing some early game MR/Armor by not buying these. But your future items will make up for this. If you`re scared of CC, you have Zhonya`s to save you.

FoN vs BV vs Abyssal
FoN costs too much and you`re not a tank. WoTA will take care of sustain. BV will block one spell, which is good, but the catalyst passive and bonus mana are useless. You will be tanky enough to take on a strong spell, especially with a shield. Abyssal. This item works on neutral camps as well as enemy minions. It`s tooltip says otherwise, but for now you can use this to your advantage. It gives you an AP bonus, which works well because you are indeed an AP carry.

Randuin`s vs Thornmail vs Zhonya`s Hourglass
Randuin`s Omen does give great stats, but it`s better off left with more Armor and Magic Resist. Thornmail, well that`s if GP or Tryndamere gets fed. Zhonya`s Houglass will let you get away with more mistakes by making you invulnearble. Once you have