Hi, im Rusin, Otp morde in platinum. Ive been playing Mordekaiser since April, i get to platinum 2 from silver 1 playing only mordekaiser top. He is not that great in this meta but my guide will give you every information needed to play him at decent level in low elo.

You can ask me, why even consider picking this champion, when its not even good rn. Answer its pretty simple, I dont know any other champion which can carry low elo players as well as mordekaiser. His teamfighting abilities in my opinion are one of the best in the game, every skill has AOE damage, while Darkness Rise deals % dmg, with liandry and rylai it will deal 8% of enemy max healh per second, thats why tanky match ups are the best for him.

Always take Flash + Teleport, you can consider taking Ignite or Ghost
instead of Teleport but dont do it, they are useless

Runes are Very big changer in mordekaiser's gameplay, Conqueror gives him ability to win fights that he shouldnt, with Phase Rush you can win range match ups and Grasp of the Undying can make your AA very powerful.
When versus good match up, you should take Conqueror with Ravenous Hunter to give you a lot of healing in late game.
when playing versus bad match up, take Conqueror with Resolve
If you are against ranged toplaner, take Phase Rush to start a fight.
Grasp of the Undying is good only with tank build.

To start off, Nashor's Tooth is the main core of my favourite build. This item gives you huge powerspike and makes mordekaiser a true 1v1 beast, but dont forget about CDR and huge portion of AP. Then you should build standard items, like Liandry's Anguish , Rylai's Crystal Scepter , Zhonya's Hourglass and some tanky items, for example Spirit Visage.
If you are behind or when you are playing versus bad match up, build Liandry's Anguish first, then Rylai's Crystal Scepter and next 3 items are flexible.
If tank is needed, build Liandry's Anguish then some tanky items, like Sunfire Aegis or Spirit Visage
Death's Dance is really broken on mordekaiser, 15% healing , 30% dmg spread over 3 seconds and some resistances are also ok, AD doesnt scale, but you aa a lot so its ok to have some.

Well, lvl 1 and 2 are not that great, you should not try to fight. When versus early game champion, dont even try contesting the wave. Just stand at safe distance and catch exp. Level 3 is a checkpoint when you can start to do something. Poke your enemy with Death's Grasp + Obliterate combination, if he wants to you can consider taking that all in (thats why you need some match up knowledge). If you level up 6 first, Take R and all in. Theres no way you are loosing. If he has lvl 6 faster than you, dont attack, just stay and wait for lvl 6 to use Realm of Death. Match up knowledge is required for lvl 6 all ins, after you played 50 games, you will know which fights are good, which bad.
If you gained some early lead, it would become easier to snowball, Ult your enemy whenever they went too far.

Theres no much to say, ult the biggest threat that you can ]kill or enemy support. If you kill support fast enough this fight will be 4v5 with you having full hp and bonus stats from your Realm of Death. Try to pull an enemy adc with Death's Grasp and one shot him. its the easiest way to win teamfights. Use Indestructible to gain max value from Last Stand, so close to 30% hp. Never retreat, Fight till the end, its very important cause your only mobility is Flash so its quite hard to escape.

Basic combo is Death's Grasp + Obliterate + AA, it will proc your passive and deal a lot of burst damage.
You can Death's Grasp + Obliterate + AA + Realm of Death to start all in.
Basic trick is to Obliterate and while in the middle of animation use Flash to catch your enemy.
Obliterate is hitting units slightly behind you, it can be usefull when in melee range.
You can Flash + Realm of Death if you know you dont need Flash to kill your enemy.
Sometimes use Death's Grasp in the front of you to disengage when you dont want to fight.
At lvl 6, dont be scared of ganks. In the least favorable option you should make 1 for 1 trade.
Always orb walk around your enemy, if you predict him to go under turret, AA then go
in that way, AA again and again, its so much better than just rightclicking your opponent.

Playing him well in low elo = free lp till plat, just master him and get out from silver/gold easily, try to not throw games and i guarantee, that he will take you to rank that you want.