CHARISMA

Your charisma score determines how many followers your character can control. Followers take the form of charmies, conjurees, and mercenaries. The maximum number of power levels of followers is determined by your charisma:

maximum pet follower power levels =
   (CHA / 10 + (pet mastery i+ii+iii+iv+v skills) / 200) * your power level

For example, a level 120 mage (power level 140) with a charisma of 14 and Pet Mastery I at 85% would be able to have (14/10 + 85/200) * 140, or 255 pet power levels. This is enough for 5 level 50 followers, or 2 level 100 followers and 1 50th level follower, or any other combination of power levels that adds up to 255.