Not Updated For Current Season
I just have to start off by saying that I absolutely LOVE morde.
I don't really have that much time to do a long destricption, but I will when i get time. I am on lunch at the moment and only have 10 mins :).
Early game you want you want to take mid or a lane by yourself. You can harass even two champions with siphon up while hitting their minions to keep up your shield. Lvl 2 you can start putting sheilds on your minions to harass the melee champs that come up to try and last hit them. when you get enough for Sorc shoes, you will want to recall and grab them and harass even HARDER. At 6 you should be able to net a kill or two, if you play him correctly that is.
Mid game I always get a sunfire ( used to be 2 but not now) and a FON as fast as possible. If you are doing really good, and not need high tanky items i normally get the abyssal scepter for more damage and some more magic res. If not see what type of team you are up against and go from there. Lots of physical, get a randuin's omen or thornmail. Lots of magic, get a banshee's vail or hextect driver.
Late game. You would like to get a frozen mallet SO you can have some type of cc. A frozen or Rylai's Scepter is always a good item to have on some that don't have a type of CC. After one of these, you become a good tank being able to slow an attacker on one of your carries. Yes you are a carry also, but your main role would be as a tank. A BATTLE TANK.
I hope you enjoyed this short description, but I lack the time for a longer one lol. Please comment and give suggestions, so I can change what needs to be changed. Thanks everyone for your time.