Mordekaiser is a tanky spellcaster, with a lot of in-lane sustain and power. He is overlooked because he appears to be a complicated champion. A melee mage with abilities cost health, and has a shield based on damage he deals? He lacks the amazing burst power of an Ahri or a Syndra but he can still win mid or top with good play.

Lategame, he can be a mage who runs in on the front lines, dealing tons of damage and protecting the AD carries so they can do their job. His shield along with his ult can keep him in teamfights the whole way, even if the team focuses you.

PROS:
Very tanky
Excellent sustain
Shield renders him unpokeable
Counter to many annoying mids, such as LeBlanc and Cassiopeia
Able to pave the way in teamfights

CONS:
Zero CC, requires Rylai's to have at least a slow
Difficult champ to master
No escape mechanism
Hard to harass long ranged champions Lux, Caitlyn

For my runes, I think defensively with my glyphs and seals, taking flat MR glyphs and armor seals. The reason I take both is that AD mids are becoming increasingly popular, and you wont be able to switch your runepage once you're in. The flat MR will help you from level one, and you will get plenty of magic resistance from a Banshee's Veil.

I think the same with my masteries. The 9/21/0 mastery set is the best this season. The Rejuvenation Bead start + 5 HP potions will give you enough to sustain your abilities.

Flash is absolutely a must for most champs. It can set you up for a kill, it can get you away from a situation where you can be killed, it can get in the way of Ace in the Hole to potentially save an ally, it's an amazing skill, despite the fact it's nerfed every chance Riot gets. Considering Mordekaiser has no other means of escape, it will be your best positioning skill. Ignite paired with Children of the Grave can give you enough damage over time to secure a kill, and give you a nice ghost to push a lane or win a teamfight.

I start with a Rejuvenation Bead and 5 red potions, along with a ward. You shouldn't be farming with your abilities all the time, but in a situation where you can get a few minion kills or a harass in with your Siphon of Destruction, you can recover the health cost much faster. With sight on one side of your lane, you can be aggressive toward the side you have sight coverage on.

Get your boots and spell vamp quickly, then focus either getting Spirit of the Spectral Wraith. If you need defense against an AP mid, grab a Spectre's Cowl and if you need defense against an AD mid, get a Seeker's Armguard.

For this core build, I make sure to get the 3 defensive stats and a hearty amount of AP. The Banshee's Veil is one of the best items in the game, and will give you more sustain. The Zhonya's Hourglass can set up a clutch play if you're getting focused and need to buy time. Rylai's and Liandry's Torment together make for a ton of constant damage, and will give you HP and AP at the same time.

I always have my Siphon of Destruction maxed at 9, and Creeping Death by 13. Siphon of destruction is a good farming tool, harass, and the best at getting your shield up quickly by casting it at a cluster of minions. Creeping death will gives you armor and MR, as well as an AoE magic shred around you. In duels, you'll be tankier and gain a lot more DPS. That along with using your Mace of Spades every chance you get will let you win one on one matchups. You should obviously take your Children of the Grave at level 6, 11, and 16, and use it to pick up kills if they flash away.

Usually, you don't draft your mid champion with the first pick, or you can be easily countered. Lots of people feel confident they can win mid with LeBlanc or Twisted Fate, but Mordekaiser can beat them both. The only mids I'd ever be concerned about are Zilean and Yorick, as Yorick can sustain just as well, if not better than Morde, and Zilean can zip in, bomb-rewind-bomb, and zip out. Morde's range cannot compare to either of them. Anyone else who gets close to burst, they will pay dearly for their attempt to kill you.

Always ward when you're going to be pushing against the tower, which you should be doing. If your jungler is going to buy an item like Wriggle's Lantern, ask them to ward the bush thats on the side of the enemy red buff, which is where most ganking comes from. Ward the other bush. 75 gold can potentially be the difference of life and death. If they have a stealth ganker, like Twitch, take a vision ward of course, and if you are crushing mid, there's gold all over the floor, and you are confident you wont die, go for that Oracle's Elixir. If they don't have a jungler/roamer, then save your money.

While laning, it's ideal to benefit from the bonus monster damage on Spirit of the Spectral Wraith and take either Wraith camps if you're mid or golem camps if you're top purple side. The best time to take them is if the minions are pushing to the enemy tower and aggressively sitting at that point would be dangerous due to a strong jungle presence. The gold advantage that you can take while the enemy mid laner is at their tower defending will help you get and stay ahead.

Morde's role in teamfights is as a front-mid line damage dealing tank. He can use his Creeping Death on himself or the primary tank for shredding damage and tankiness. You want to drop your Children of the Grave on their AD carry and kill him quickly, and control his ghost to melt the rest of the enemy team. His peeling potential is minor as he has no hard CC, so a team comp that features a good peeling support would best suit Mordekaiser.

Mordekaiser is a powerful tanky spellcaster, who can initiate teamfights, deal tons of damage, and pave the way to victory. He can counter many people mid and top, and push towers quickly. He can be tricky to learn, but within a few games, you should have a rhythm going. Mordekaiser best thrives on a team where other members can use CC while he focuses on killing the enemy ADC and using the ghost to his advantage. I wish you all good luck, and I welcome feedback.