Hi, well, Morde is my main, I played a lot of games with him and i mostly have only victory lately with this build, so i decided to share. It will not be an in-depth guide, I will give all the tips I have gathered, period. First I have to say that I started with the revamped build of frish, and then from game to game slightly go to an ap/offtank build.

Pro
- Very good one on one
- Heavy farmer (level 7 you eat a creep wave in 6 sec)
- Squishy champion eater
- Very good harass (only if you understand that your [spell_icon=siphon of destruction] as a great range)
- Once you buyed life you CAN iniate fight

Cons
- If someone take you without your CDs you will be dead
- With this build, morde is not extremely solid early/earlymidgame and get killed easy against if stunned

Iron man (passive) : So, from lvl 1-4 your shield if full can take a tower bolt without attack your life and, after that its towerdiving madness, every time its full don't wait to loose it, 3rd skill on your enemy, take the tower bolt, back off and wait for minions to come.

Mace of spades (Q) : I max this skill last, but its grat tho, late game its your most heavy damage skill, with lichbane and 500ap, you ashe at 1.3k. Certified

Creeping death (W) : Truely love this skill, you farm, you AOE, and you are protected put this on you when you go melee/near your enemy. The more they are (minion and/or champion) better its work, just remember you are not a tank (specialy early game)
TIPS: I have noticed that when you have difficulties and cannot get nearby the minions you can still farm and stack iron armor by launching this skill on the THIRD MELEE MINION ( why? because he is the one that is less focused and go between sorcerer and melee oppenent minions=more dmg=more armor=more farm)

Siphon of Destruction (E) : Max first, its just a cheated skill, beware to launch it on many people as possible, even lvl 1 if you manage to launch on all the minions of a wave you will have almost all your iron armor.
Its cool for harass, PLZ REMEMBER IT ACTUALY HAVE A VERY GOOD RANGE, train on minions, but once you are fully aware of the range nobody will escape you (not even nidalee :)

Chidlren of the grave (R) : With AP/Magicpenetration/Ignite, you take down anyone, and i said anyone, better to launch it in fight because sometime people forget how much its hurts, and it also heal you (a lot if you have spellvamp, and you will) and stack iron armor, but if you see a low hp under a tower and there is minions nearby, stack your armor and go for it you can take easiky two bolt and your ulti as a long range.

Farming is essential to pull this build out, its really expensive so make sure ta hit all minion very hard, spam your E on them, and put W if there is nobody coming for you.