Another build made with help from Janitsu as i'm not used to play with mordekaiser so some thanks to him for helping me out again by testing it and giving advise ^^

This build is focused on mordekaiser as an AP/tank meant for 5 vs 5 games.

Since we're making an AP tank we focus mainly on health and ability power, health as you'll be tanking and Ap to increase spell damage and refill your shield faster. As last addition we add some magic penetration to make your spells more of a problem for your opponents.

For masteries we start with adding ability power, cooldowns and magic penetration which is used for every Ap build and we finish things off with more health, health regenerate, armor, reduced damage, ect. which is used by a tank build. An extra usefull thing is the ardor mastery which increases your ability power by 4% through the game.

OK we start with the normal tank itemfor increased health making you already from start harder to kill due to all your health boosts. Now we just support our partner and defend the turret while gaining money. Once you got enough time and gold to upgrade , you return to base to upgrade the stone intogiving you more health and passively more gold over time. We keep defensive while supporting our partner as we raise our gold by farming minions and of course assists. Now when you return to base you buy awhich you soon upgrade into afor increased spell damage, more shield power and spellvamp making you harder to kill and making you deal more damage. Now depending on the team and your opponents you either rush forwhen you're winning or go forto support your partner by slowing your opponents making them easier targets. Later on you go for the other one of the two. Now we upgrade your revolver into thegiving both you and your team more ability power and spellvamp. With 2 more items to go and a decent Ap damage we can now go for the second part needed for the omen shield, namely thegiving you a chance to slow opponents who attack you aswell and bonus armor making you a troublesome opponent to fight as you slow them either with spells or your passive. Now we first go for a last item as we still have the passively increased gold from our first upgrade. Depending on your opponent we either go forfirst if we're against a meelee based team orotherwise as it regenerates hp constant and increases your magic resist when fighting mages. Now we finish ourfor a usefull slow ability and increased health and armor. As last we finish by picking the other one of the two you picked before ( eitheror the)

exhaust: to keep them into your teams reach or to help getting your team the upper hand in a team fight.

ghost: for chasing opponents so you can slow them with your spells getting them back into reach of your team.

Other usefull spells: ignite, cleanse, flash, heal (but heal isn't really needed as you got spellvamp and shield)

pro's:
- alot of armor and hp combined with his shield makes him one of the strongest tanks
- keeps his strong abilities without losing defense
- can multislow enemies by either using spells on them or letting them attack him
- can take the lead in a team fight
con's:
- takes time to become a real 'iron shield'
- weak early game
- hard to master
- expensive items
- slow as he got no boots

As you can see this build gives you alot of defense without lowering your spells power , making it a very deadly combination with your shield. I hope you found this build usefull, any feedback is welcome so feel free to comment down here ^^