Hi i made this build and guide to show u that ad mordekaiser is playable and even stronger then simple ap mordekaiser, your q are destroying every champion 1 vs 1, even tanks like mundo. Only thing you are afraid of is stunts, you can carry every game even if u are loosing 1 : 20. Enemies are always suprised when their hp ale falling from full to 1/4 in one hit. I'm making guide for first time so please forgive me for spelling and mistakes, this is not troll build, it's way to suprise your enemies and carry your team to victory animation. And most important its very fun to play ad mordekaiser. Very sorry for my poor english :/ . I will try to correct this in my free time.

Movement speed is very important for you. You will be chasing enemies running in fear, clearing waves of minions in 2 seconds, clearing jungle in mid and late game, boots of mobility + enchantments.

Vampiric scepter - next important item for you, your skills are eating your hp so get this item as soon as possible.

Statikk shiv - 40 % attack speed, 20 % crit chance, 6 % movement speed and powerful passive, clear every waves of minions and makes gold for your next item - Ravenous Hydra.

Ravenous Hydra - made of vp and tiamat, you have hp regenerations, life steal, 50 damage, passive ability and even stronger active, teamfights are very painfull for your enemies

Infity edge - you will need crit chance so buy cloak of agility first

Phantom dancer - movement speed,crit chance and attack speed, they cant run from you.

Last item, depends on your choice or type of your enemies

Bloodthirster - tons of damage

Youmuus' ghostblade - chase them faster! kill them faster! cdr (you need this for spamming your mace) , ad, as, movement speed

Hextech gunblade - ap, ad, spell vamp, life steal, passive guarantees refreshing active fast, VAMPIRE MORDE

Trinity force - all what u need

Warmog's armor - immortal?

Rabadons deathcap - you make now more ap damage

Frozen mallet - stop, hammer time!

Lich bane - why not? ap, movement speed, passive ;D

Max q first, then e, w last

Flash + ignite are standard, u can try with cleanse and ghost to be unstoppable unstoppable, exhaust and teleport can be usefull too

Pros:
+pusher
+farmer
+killer
+great in teamfights
+can carry the game in every situation
+tons of damage
+can destroy every kind of champion

Cons:
-kind of squishy, but your passive
ability makes shield, so you are hard to kill
-your teammates can be mad
-very sensitve to stunt, slow, etc

You are made for farming, speed and clearing waves and amount of gold that u get from this allows you to buy expensive items very fast and push/defend towers even in 1 vs 3 situations. If u cant get new wave of minion go clear blue, red, wolves, wraiths, golems, or dragon.

Your teammates can be mad for "taking" red or blue or blame you for trolling, but when victory animation appears, they can not deny that you drove them to this point