This is a build to a powerful 8 foot tall Mordekaiser, tanky, and dps. With this build, depending on which items you build, you will be able to take on a whole team. Please, enjoy.

For the runes, the 9 marks of magic pen are a must for Morde if you're going to harass early game, who wouldn't. For seals you can go just about anything you want, either dodge, armor, or magic resist, any would work fine. I chose those 3 types of seals because the dodge would have a better chance to proc the talent Nimbleness, the armor and magic resist come into play if you feel like your chances going against an AD/AP character are high. With the Quintessence of Fortitude, you gain quite some health which is also nice early game, and helps later in game a bit too. With the glyphs, either CD reduction or MR are good, I choose these because its nice to have less of a CD on my syphon is really nice, and if you want to go more tanky, the magic resist is really nice to have.

Usual tank talents, 9/21/0, you might find yourself saying, why doesn't he have talents into Mender's Faith, or Strength of Spirit, well, if you didn't know, Morde doesnt get heal first off, unless you are new to the game. Second, Morde has no mana you silly's! Also, no points into Willpower or Reinforce, because again, all good Mordes know, ghost and ignite are powerful. I'll talk about those 2 spells in a few chapters, but for the love of god, dont get fortify or cleanse.
Onto the offense tree, the AP is a nice add-on with the magic pen runes. Also, CD reduction is a nice aspect, but its optional. Then you get the 15% magic pen, also a nice addition to the current magic pen runes.

I like to start off with a Regrowth Pendent and health pot first because Mordes abilities cost health, and early game you gain the health back quick, more harassment. Get Sorcerer Boots next followed by a Giants Belt, which you can either turn into a Sunfire or Crystal Scepter, depending on what you want to go. After that I would usually go for a Negatron Cloak and turn that into a Force of Nature, for some magic resist. People usually ask me, why not go Banshee's, the only thing useful from Banshees for Mordekaiser is the MR and one blocked spell, but Mordes shield can block a spell pretty good, and the HP regain/ movement speed increase is generally better for Morde, because he usually is around 385 speed with boots and no other speed increase, and 416 with boots and FoN, so you can catch up or escape quickly if needed. On to Guardian Angel, Morde having a second life is just really good if you couldn't finish off a character, just get back up, brush yourself off really quick, then go mess them up. Thornmail is for the annoying AD chars that just wont get off your back.

Pretty simple as the skill sequence shows above, I like to max my Siphon out first, just because it does damage, but early on I go E-W-E-W-E-R just because the damage that the W soaks up in minions for your shield, and the Siphon hitting hard early with your ult/ignite just messes people up. So, max out siphon then get the next rank of your ult when you can, then just switch between leveling up mace and creeping death.

Ghost and Ignite are the 2 Summoner Spells I like to use the most, but I have tried out Tele/Ignite, Flash/Ignite, and Exhaust/Ignite. Any of those spells are a great help to Morde because with teleport you can zone in on team fights quick if you aren't there, or you have an escape/kill spell that will help you out.

For jungling/creeping, anything is good to kill, just make sure if you have a jungler, you aren't stealing this from them. Both RED and BLUE buff are beneficial, the AP helps out your spells, along with the AD, which also has a chance to slow down your enemy target.

Morde is not really considered to be a helpful tank, but if you can get all of these items, you can take out a whole team buy yourself. One way to help out your team, is to take the most damage from your team, so you a way more chance of survival than them. If you can have the opposing team focus you first, you are doing a great job, keep it up. One BIG part of helping team is using your ultimate to make a 6v4, and give your team the bigger advantage. Dont worry about killstealing in a team fight, if you help out your team, and someone cries about you getting a last hit on a enemy, tell them to please, uninstall.

The unique skills of Mordekaiser is his shield. If you charge up your shield, it will save you trips from going back to the base/store. Whenever people are about to possibly kill me, I charge up my shield, and retaliate.

Morde is one of the greatest farmers in game I'd say. With all the AoE he has going on, you kill minions within seconds. Features that help this are: Sunfire Cape, Creeping Death, Mace of Space and Siphon. All short CD, and all do a lot of damage.

This is my build to a successful, powerful Mordekaiser, I hope you've all enjoyed it! Thanks for looking and good luck in your games :D