Well for the start
Hello and welcome to my guide of Morderkaiser.
Right in beginning i have to say "sorry for my bad english"(I have only 12 years ^^)
I hope you will like it! :))

Well i pick these runes cuz morde abbiliyts need his health thats why u need health regen and he need health too for that.U need Quintessence of Swiftness cuz morde isn't fast

First i most like morde when he go solo so at beginning he need dorans shield to stay longer in lane.

Then when you first time recall you have to get Sorcerer's Shoes,then you get extra magic penetration.Afther that i recommend to buy Rylai's Crystal Scepter
but first when u go to buy it first take health and then abillity and other stuffs(just to stay longer in lane).This is item i most like Hextech Gunblade.Its very good bucose morde have high health and when you have lifesteal his very hard to slain.Then to get better health and health regen i recommend Warmog's Armor.Afther that i get Force of nature then Morde is very strong.Then for last item i suggest Lich Bane.

Well Siphon of Destruction is my first skill cuz u can hit target easy.I get this skill to max right at beginning.I upgrade Mace of Spaces at level 2 only reason is that i can't hit 4 targets.Afther Siphon of Destriction i upgrade Creeping Death.This skill is very good for farming.And finnaly the reason i buy Hextech Gunblade is bucose of my ulti children of the grave which is one of my favourite ultiys in LoL.

Like i sad at beginning morde is so much fast that why u should take ghost.And ignite is the perfect match with morde ulti.

I most like to farm with Creeping Death and Siphon of Destruction.Like in LoL build Morde is very very good pusher