The idea behind this build it to use spellvamp in place of heath regen to get around the fact that Mordekaiser uses health to cast his abilities. This also allows for Morde to have an almost tank like quality in the late game as you will simply gain your life back as you rip through the opposing teams champions at up to a 3v1 fight. This build has had me turning 30+ death deficits around in seconds as entire teams ran from me.

The marks allow you to deal quite a bit of damage early game as any magic resist they may have gets taken away by your spell pen.

The seals of defense and the glyphs of magic resist are for survivability in the entire match.

The Quints in ability power give you a little extra kick in the early game to help with initial kills

Setting up the masteries in attack allows for cooldown reduction and spell penetration for all of your abilities

The masteries in defense give you survivability along with extra health and ability power. It's a shame that you can't also get a point in tenacity to give yourself 5% reduced damage overall but that's an option if you feel you need more defense in place of magic penetration.

This build has a few variations that allow you to dominate in every aspect of the game.

If the opposing team has an Attack Damage champion (or champions) that is (are) giving your team trouble (aka, running around ganking at will, pushing towers, and all around wreaking havoc) it is 100% NECESSARY for you to build a Thornmail ASAP! for me this normally happens right after I get my Scorer's shoes or when I have just started my deathcap. It's only 2000 gold and since the AD champion has been winning he'll be cocky and try to kill you only to find that none of his attacks can do any damage through your shield and massive defense. Building the thornmail will only mean that you get 2 Gunblades instead of 3 and that's not the end of the world for you, but it will devastate the opposing team

If the opposing team has a Ability Power champion (or champions) that is (are) crushing you with their amazing spell casting, it's time to give yourself the edge with some magic resist. this can be in the form of an early Lich Bane (though that's only 30 magic resist and might not do enough for you) or you can build a Force of Nature (this will give you health regeneration along with your spell vamp making it near impossible for you not to be at full health all the time). Banchee's Viel is another option though the manna aspect makes it less desirable. Again just sacrifice one of your three Gunblades or the Lich Bane for the in game item switch.

If you don't see a point in having 3 Gunblades and want more ability power and a little bit of Crowd Control, a Rylai's Crystal Scepter is an amazing addition to this build and should be added directly after building your second Hextech Revolver

I believe I put the skills in the right order but in case I didn't there's a very simple way to remember what to do in 4 easy steps.
1. GET YOUR E. This is your main harassment tool and the primary way to get your shield up.
2. When you can't get E, get your Q. This is your heavy hitting ability as it adds up your ability power and attack damage (you'll get attack damage from the gunblades too) and hits an area for upwards of 1000 damage by the end of the game.
3. Get your ult whenever you can, this is what makes Morde amazing. the burst heal from casting along with the spell vamp from the damage dealt will save you in the early seconds of that 3v1 I was talking about as the opposing champions spam their attacks at you.
4. After your E and Q are maxed at 5 get your W up to it's final level.

Ignite is to be used with your ult to kill the opposing champion as they run away. Morde is very easy to run from as he has to Crowd Control.

Morde is the MOST effective farmer in the game in my opinion. The AOE style attacks allow you to slice through waves of creeps in seconds and get the last hits on all of them as soon as your damage output becomes high enough to kill them outright. My technique is to start with a solid hit with E, followed by a Q hit to the first line of creeps, then use W on yourself and walk to the second line of creeps to auto attack. As soon as your abilities are off cooldown, repeat. Farming also keeps your shield up so that its harder to kill you.

Mordekaiser's Ultimate is one of the best in the game as far as I'm concerned. It heals you, deals damage both initially and over time, AND if you kill the opponent while your Ult is on them you get to bring them back on your team under your control. With this being said, ATTACK DAMAGE CHAMPIONS ARE YOUR TARGET. I can't tell you how many times my team has been loosing to a Xin Zhao or a Twisted Fate or a Yi and by just killing that one champion and bringing them back on my team we were able to score an Ace. No one every expects to have to fight the super fed AD champion on their own team. You can even control the ghost by holding down "alt" and clicking the ghost to attack towers or champions. Nothing better then having your ghost tower dive his own team for a kill. one thing to note is that before you use "alt" to control your ghost for the fist time the ghost will attack whoever you are auto attacking but after you use "alt" you have to continue to use "alt" in order to have the ghost attack who you want them to. Controlling two champions isn't too difficult but it takes some getting used to.

Ghosts are perfect for tanking towers for your team or checking corners or harassing while you move somewhere or kill creeps.

If you move too far away from your ghost it will teleport to you. This is useful for saving the ghost from being killed in a tower dive, simply have the ghost dive, and then run away from it if it looks like it's loosing and it will telly right to you.

HUGE NOTE! If you are in tower range and your ghost attacks an enemy champion, the tower will attack YOU. Don't let yourself die to the tower because of your ghost, this is never fun.

Early game:
Harass with your E to keep your shield up and your lane opponent at bay. Morde can both mid and side lane with people so take your pick based on what you're comfortable with. Be careful with your health before you get your Revolver. Your spells take health to use so you're killing yourself until you get it. Try to get it as soon as you can and then get back to your lane. Life becomes much easier after that. If you do have to back before you have enough to buy the Revolver then buy more health potions to keep your health from running to 0 on account of your casting.

Once you have your deathcap or at least your needlessly large rod you have the power to start killing off people. At this point you should have a tower taken down so find a lane and go gank. try to come in from behind your opponents as this will give you the most time to use your attacks on them.

Team fight mentality:
1. Use your W as you start to come into the fight, this will activate your Lich Bane and give you more defense and magic resist for the fight.
2. Hit with your E on the whole group of opponents. This will max your shield and deal a good bit of damage.
3. Use your exhaust and your Q on the champion you're trying to kill, this will deal the most damage and slow them down.
4. Use your Ult and Ignite on your target, this will heal you back towards full health as they have probably tried to kill you and you will have most likely taken damage.
5. Continue to spam your attacks on the group until you get a kill, they retreat or you are forced to retreat.

If you get the kill use your ghost to clean up shop or take down a tower.

Late Game:
Stay with your team. Your opponents should be terrified of you by now and thus it will be harder to get kills on your own. Always come to the aid of your allies if they are about to get killed. most of the time you will be able to save them. Your W can be used on your teammates to give a tank an edge or keep a squishy from dying.

Hope you enjoy destroying your opponents =)