Ok... I can help you with this but I won't do it and simply give it to you. I'm busy witht he hero contest. I'll give you advices. Let's see... You will need to base this spell upon Storm Bolt. First of all put only ONE level, levle 6 required and change icon if you like. Give it NO damage and whatever missile you like. Change the duration to 17 for unit and whatever you want for hero. You could make 17 for hero as well (Oh, hope this is an ultimate).
Now, we go to trigges. It's kinda difficult to make the caster Mirror Image himself. Still, you can make dummy units. Dummy units are units that have Locust Skill, as much mana as possible, no food cost and obviously not a worker. Base it on footman let's say and give it 0 movement speed. Make them look just like the hero you base the spell on, give them 0 to green and red for coloring and give them Blink ability and Mirror Image (both of them Neutral Hostile... So not hero skill). Still, we will need to make a Blink that has no cooldown so you can complete the circle. Copy the blink, change its mana cost to 0 and its cooldown to 0 as well. Copy Mirror Image as well and do the same thing (no cooldown or mana cost). A last skill to copy is fireball. Copy-paste it as well and change its stun to 0 and its damage to how much damage you want the images to do. Making them give the damage of the hero is relatively hard. Experiment with the skill a little so that it does the explosion effect on the caster. Change Target Animation or something... It's the best I can do for this. Ok, now let's go to triggers. It will be pretty complicated and I hope you can handle triggers. I will just guide you there as well.
Triggers
Ok, the first thing to do is make a trigger which starts to work when your skill starts its effect. Now, hide the hero and create one dummy unit you made, at let's say 150 range from the position of target unit of ability being cast, oh and 0 degrees. Now, you will need to make a FOR from 1 to 35 in which you get a real variable (blink_real let's say) with the starting value of 10. Order the dummy unit to move at position of target unit of ability being cast again with 150 range and "Blink_Real" degrees. Wait 0.10 seconds and then set variable "Blink_Real" to (Blink_Real+10).
Ok, you ahve the circle. Now we need to create FIVE dummies. Remove your dummy unit and create five dummies at position of target unit of ability being cast with 150 range. The degrees must be at difference of 72 between each other. So create dummies at 0/72/144/216/288 and the stuff up. Add all the dummies to a group, maybe called "Mirror_Group" or something like that. Knowing what damage the hero has is pretty hard. That is what the fireball is skill is for. Order each dummy to cast Fireball at Target unit of ability being cast. Wait 0.10 seconds and pick up every unit in Mirror_Group and remove it. Clear Mirror_Group. They hit the target when the unit is still stunned though. You may change the stun duration so you can have the clones hitting the target just when the circle is complete.
Hope this helped you...
Daelin&