Invasion Enemy Classes

In addition to the mob types there are several different classes the Invasion ogres can assume. From the in-game help file:

Invasion enemy classes:

Each class of ogre possesses different strengths, weaknesses, abilities,
and behaviors:

   armored: These otherwise average ogres are decked out in very
            heavy armor, which renders them quite resistant to damage 
            (especially from physical sources). They have the ability 
            to extrude earthen spikes from their armor to inflict 
            painful counterattacks when struck.
     rogue: Rogues are very agile, and while they're not overly
            healthy, they can be hard to hit. They are usually cloaked,
            and can summon short bursts of speed in combat.

  The armored and rogue invaders are the primary source of heartbreak
  for the repair golems which Tyf can construct. These ogres love the
  crunching sound which the golems make when stomped on, and will
  stalk them mercilessly.
  
   howling: Somewhat larger than the armored or rogue variants, the
            howling invaders are both swift and hardy. When attacked,
            they will often summon reinforcements in the form of
            vicious mud mongrels.
 sulfurous: These magically inclined ogres can be surprisingly
            resilient, given their fair quickness and high health. 
            Their spells are quite painful, and they can also inflict 
            a debilitating hex in close combat.

  The howling and sulfurous invaders grow more destructive over time.
  They don't deal much damage to Ruushi at first, but the longer they
  live, the stronger their destructive streak grows. If allowed to
  grow for too long, these two classes can wreck Ruushi quite swiftly.

 shriveled: These ogres possess a strong level of intellect and
            wisdom, and are among the largest invaders in terms of
            pure health. They are not particularly adept at close
            combat, but they can inflict a curse of fatigue upon any
            defender within the city.

  The shriveled invaders prefer to avoid combat whenever possible;
  instead, they harrass [sic] Ruushi's defenders from afar with their
  curses of fatigues, slowing down the victim's movement and combat
  actions.

  mesmeric: Strong in the areas of wisdom and willpower, these
            ogres are masters of mental manipulation and illusion.
            If left unchecked, they will weave intricate spells to
            entrap the city's defenders in twisting labyrinths.

   meatbag: These hulking masses of muscle and putrid flesh
            can sustain quite a bit of damage. While the meatbags are too
            large to actually move without magical assistance, their
            massive belches can sometimes repel aggressors with surprising
            force.

   Mesmeric and meatbag ogres tend to do slightly more base
   city damage than the other invader classes, except for a
   "powered-up" howling or sulfurous ogre.

    shaman: Physically, the shamans are weaker and more vulnerable
            than most of the other invaders. They prefer to hide, 
            working together to devastate Ruushi through the 
            conjuration of powerful earthquakes.
   warlock: The warlocks are in some ways the heart of the 
            Invasion, transporting invaders into Ruushi and 
            protecting the Invasion leaders from detection. The 
            warlocks are always well-hidden, for if they are
            confronted in close combat, they fall quite quickly.

  Unlike the other ogre invaders, shamans and warlocks try to avoid
  entering the city of Ruushi itself due to their vulnerable nature.
  Tyf can construct a device which forces the shamans from their
  hidden dimension, while Shaker is in charge of coordinating aerial
  assaults on the warlocks' home base. Eliminating the shamans is
  the only way to reduce the damage that their earthquakes deal to
  Ruushi, while eliminating the valuable warlocks ensures that the
  Invasion leaders are eventually exposed while earning faction for
  the defenders.

For basic information about Invasions, see 'help ruushi invasion'.