First of all I want to say thank you to all of those involved in this discussion for drawing me in and entertaining my brain
My offerings on Cleave-MI RAW
PHB 173 Illusion:Figment: A figment creates a false sensation.
You believe that the figment of the caster is the caster and begin your attack phase.
If your attack is succesful, the image is destroyed. No damage is rolled.
The strike itself is enough to drop the images hp's to zero or less in that a struck image ceases to exist, and thus has no hp.
Now, the attacking character believes he has destroyed (or dropped) a creature. There is no saving throw for MI, so unless the attaker has some way of ignoring the spell all together, he believes.
Now we get into opinion. It is the nature of D&D that on occasion a character may find themselves attacking opponents that are no more solid than wisps of smoke. In that situation, where there is no question as to whether or not the opponets are creatures, the attacker may without question apply the cleave feat should other opponents be within reach. Also, I understand cleave not to be some thru attack, like cleaving thru a door, or thru one enemy into another, but a redirection of energy. *Example* Attacked enemy has fallen, the energy, thought, and strength I had to apply to defending against that creature is no longer needed..Those energies, by virtue of this feat, can be quickly redirected against another opponent within reach.
As for cleaving with a reach weapon. Attacker drops an opponent 10 feet away and quickly redirects that energy against another opponent in reach by spinning the *insert reach weapon here* by it's middle, at a angle, and shifting grip. These qualities of quickly shifting focus with long weapons are commonly showcased in martial arts films.
Now...we have a figment which the attacker believes to be a creature, that disappears when struck, which is, I am assuming here, analagous to being droppped. It has in all ways acted as a creature *might* within the rules. Does the DM then stop him and say " Your *character here* senses that what you have destroyed was only a figment?" No he does not, the spell is still active, and there is no saving throw. So even after having interacted with the figment, he still believes it to be a creature, and would act accordingly. And if in that situation, attempting to attack another creature that may or may not be a figment is a rational action, AND that character has the cleve feat, I believe that by virtue of overwhelming evidence he can, and indeed should, proceed.
I must agree that the word creature in the Cleave description negates all I have said here. But I have attempted to show other evidence from other sources within the RAW that show a contradicting view. In a situation where there is a contradiction, the errata, and I imagine, the FAQ apply. We all know there opinion on the matter.
Now... Magic Missle. The caster believes he is targeting a creature. IF the spell does not immediately fail, due to improper targeting, the missle could indeed strike a target, destroying it. Magic Missle does no damage to objects, but it does strike, and striking does destroy an image. Now... there is adjudication needed to here. Does the magic sense what it can and cannot target? Or is the casters understanding of the situation enough to get the spell cast, and leave it up to the nature of the magic as to whether it's succesful or not.
Golems are immune to charm. But that does not stop a foolish caster from trying it.
Anyway, I look forward to hearing your responses to my thoughts when you have time, and mind you, I am not trying to stick to my guns here, I am trying to add to a argument I believe has merit.