MArcomage

I think this is a good idea, considering the existence of Master of the Past and Anomaly sphere. But I think that its cost should be raised to 10-15 accordingly. And perhaps making it something other than Illusion...
On the name, I think "mirrored motion"/"mirrored action" would be a better name. A better picture would be one that shows a complete real castle (and landscape) on one side and an ethereal copy of it coalescing on the other side. Possibly with some odd divider in the middle, reminiscent of Replication.

If you wanna compare it to MotP & AS, you should keep the cost 10, since they are that price too.

True, but those are both undoing effects, this one does an effect. I thought it would be more useful, and thus require a higher cost.