Cast Gather Specimens by paying ({3} magic symbol) ({U} magic symbol) ({U} magic symbol) ({U} magic symbol) , causing all creatures that would be created under an opponent's control this turn to be created under you control instead.
Cast Fractured Identity by paying ({3} magic symbol) ({W} magic symbol) ({U} magic symbol) , targeting any permanent.
Dualcaster Mage enters the battlefield, creating a copy of Fractured Identity, targeting Dualcaster Mage.
Resolve the copy of Fractured Identity, exiling Dualcaster Mage and creating a copy of Dualcaster Mage for each opponent you have.
The Dualcaster Mage token(s) enter the battlefield, creating a copy of Fractured Identity targeting Dualcaster Mage, and any other instants and/or sorceries on the stack.
Repeat from step 5.
You may also have the additional triggers target permanents your opponent control to exile them and create token copies of them.
Results
Exile any number of nonland permanents.
Infinite copies of any instants and/or sorceries on the stack.
Infinite copies of any nonland permanents on the battlefield.