One of my favourite champions is Mordekaiser and i like him too cause ha has his abiliteas and passive named by my favourite songs,he as great solotoper-tank ( but he can also be and great AP caster) you can play hom too on mid.
I crated this build cause every one is crying thath Mordekaiser is too much nerfed i say no he is still good

PROSGreat solotoper
Does tons of dmg wven with low Hp
Great ulti
Good spamer with E
Names of songs on his abilities
He has an Morgenstein
Great passive shield
Every his skins are cool :D

CONSWeak at start
When you dont buy any resist,hp,hp regeren or spell wamp youre usseles
His abilities costs Hp
Not so good vs Ad carrys

i take like all tanks and ap magic penetraion marks.
on seals i take armor so be more tanky or hp per lvl its good too and most recomendet on solotop lanes or to spam yor spells. you can take too 5.35 hp runes but i dont use them so much.
for ghlyps i take the potency for ap power so i can do from the start TONS OF DAMAGE or the cooldown runes for spaming my spells
for quintenssences i take like for all ap 4.95 potency runes and for the tanky i take 26hp or hp regeren for good survability.

for both builds i take 9/21/0 why ? cause you rly dont need so much ap power or spellwamp movement speed mana death reduction or cooldown.
9 in offense is for ignite and ap with cooldown
21 in defense takes you good survability,you are more tankyier so you dont need tank runes, you dont need summoners resolve for ghost cause intiator buffs you movement when you are below 70%hp and you shure will great chase low hp champions ( CARE TO NOT CHASE SINGED !!!)

My 1st item is dorans shield cause it gives you armor,hp,and hp regren
you can also take regeren pendant or boots.
Like all others 2th item are boots for movement speed
3rd item is hextech revoler for spellwamp
4th i take Regrowt pendant for Hp regeren
then i take hextech gunblade for spellwamp and active you can slow your enemy by chasing or when he has low hp to kill him or to slow an enemy to run back
rylais scepter is very important for hp and slow
then i take force of nature for resist,movement speed and hp regeren
i full do my boots too sorcerers shoes for speed and magic penetration
rabadons deathcap for tons of dmg :D
abbysal scepter for resists and ap with lowering enemyes magic resist
you can also take zhonyas for armor and ap so you dont need to buy abbysak cause you have allread magic resists on force of nature

the main dmg dealer is E so max it first (not cauting ulti it will be last) and it does AoE
the 2nd spell for dmg is Q, its great you you can by a minions do Q it can split in 3 so the 3rd reaches and enemy champion to kill him :D but it does more dmg on one target
last i max W it gives resist and does AoE dmg like E, now it grants you too assists so if you cant reach an enemy with low hp you can get to like Warwick cause he gets speed from low hp enemyies you shield him with it so it does dmg and resist by passing turrets
And one of the best ulties Children of the Grave (its an great song too :D)you can by the start of focusing the most dmg dealer of the enemy team so your team mates kill him 1st and get his clone thath you can conrol him like Vayne she does tons of dmg yo get her clone and pupdada you get several kills,you can also use it for last hiting on the enemy champion soo he dies or when he runs use it (cause it has and great range) to slow him with rylais scepter

2 best spells ignite to kill your enemy (its very good with your ulti allmost same range)
ghost to run back or to chase an enemy
flash can be too used but i dont like it now so much its nerfed hi range long cd, but you can also use it
heal to when you have no hp
cleanase when they have an stunner or slower

as Mordekaiser on solotop or mid youre such soo good like stacking nasuses Q you even dont need to last hits with your normal attacks your Q and E does it they have an short cd so you can easily farm
i can even take the dragon solo on lvl 5.