[Shostak]

Creating illusions can be extremely effective, and their lack of maintenance cost offers a distinct advantage over summoned beings.

Despite being able to be disbelieved, illusions can still be effective against foes with very high IQs, like dragons. Each turn they spend disbelieving is a turn they don’t spend dealing out damage. And, if they don’t disbelieve, the illusion can try to put some hurt on them every turn it remains. Keep creating illusions and soon the dragon is overwhelmed by your real and illusory friends.

But illusions do have their limits. Summon Myrmidon can bring a warrior with a missile weapon that can actually be used, but illusion can’t, since illusions can’t be split. Moreover, many GMs will declare an illusion of a warrior disappears on a break- or drop-weapon result.

Note: by RAW images can’t be disbelieved, giving them some tactical advantage over illusions despite vanishing upon contact.