Nashor's tooth should be labeled as an essential item on the Recommended set for Mordekaiser.

The attack speed and AP makes it IMPOSSIBLE to win a trade against morde. EQ the enemy, Pop W sheild and start swinging. Since Mordes abilities have a decent amount of cooldown early, it makes for much easier trades for you, and unwinable trades for them.

Just played with someone doing this in mid against a zed(Zed was gold 3 and morde was silver 2) and morde went like 9/0 in lane, and even got a tripple kill when jg and support did a gank together, The amount of healing he gets from being able to auto at such an accelerated rate is just ridiculous. End of the game he was 17/2/13, with better CS than our adc who just split most of the game. He said hes not a smurf...

So either morde is super overtuned or Nashor's rush on new morde is broken.