Illusionist
The Illusionist doesn't have all that much going for it at low levels. They have low health, relatively low attack and don't have many abilities. Their Mind Shield protects against only a small number of psychic units, who besides Mind Rippers and Unholy Reavers, simply aren't that powerful or common. Their Mind Blast power does relatively little damage and can be resisted. They do have the benefit of being rather cheap, however. If they are leading a group of Mind Rippers they will also give it an efficiency bonus.
But people buy Illusionists for the dream of their best ability, Illusion. It's a dream, because unless you get your hero from an artifact or God's Most Favored, it will be at the most 17th lvl, and Illusion is an 18th lvl ability. From what I can tell, Illusion is totally random in that it picks any of your stacks and duplicates it 200,000 net power per level of Illusion (so 200k at lvl 18). If you are deep stacked, this could be less beneficial, as an extra 200,000 Squirrels isn't nearly as benneficial as an extra 166 Efreeti.
At higher levels, the Illusionist becomes extremely powerful indeed and could be a truly powerful weapon. At lvl 20, it will create an extra 15 Dominions or 12 Titans, for instance! Since enemies generally attack lower than themselves when trying to grab land, you've essentially added an instant 600,000 net power of pure troops. This can be especially deadly at lower ranks and for catfishers (people who purposefully stay low in net power to try and kill targets who are injured) where such a boost in net power could be a large percentage increase.
When it duplicates a unit, it is added to your army as an additional set of troops and not combined with what it copies. That also means the enemy can easily waste an attack or more trying to destroy it, when it has no impact on the outcome of the fight. For example:
ARMY BEFORE ILLUSION
Dominion 45
Titan 36
Archangel 598
Unicorn 696
Sheep 32593
Preacher 1243
ARMY AFTER ILLUSION (TITANS RANDOMLY CREATED BY LVL 20 ILLUSIONIST)
Dominion 45
Titan 36
Archangel 598
Titan 12
Unicorn 696
Sheep 32593
Preacher 1243
So I would generally avoid an Illusionist if they are low level and you are not Blue, or plan on having Mind Rippers they can lead. But a high level one early in the game can be very nice.
