Not Updated For Current Season
The masteries shown here are not yet updated for the current season, the guide author needs to set up the new masteries. As such, they will be different than the masteries you see in-game.
Mordekaiser is my favourite tank and he can - played right - dominate every game, even with nearly no ability power.
The best item build is different in every game, you have to to watch you enemys items all the time...
This build is made for a mixed enemy-team, and with it you should be able to initiate and survive every team fight. Please try it out and tell me what you think about it :)