Steel Skull

Roll a D6 at the start of the game and constul the chart (Pg.25 Codex Orks). This establishes the maddness for the Madmob. The mob is subject to the psychology rule indicated from then on.
At the start of each subsequent turn the Ork player rolls a D6: On a 1-5 nothing happens and continues with its last roll. On a 6, you roll on the chart again to determine the maddness.
Should the Madmob be broken, then a new maddness is established as soon as it ralies.