For more rulings concerning the Burst Area, check out Burst.
Mirage (ミラージュ) is a game mechanic debuted in SD59 and BS56. It is an effect which Spirit cards, Ultimate cards, Nexus cards, or Magic cards may have. Cards with Mirage are placed face-up on the Burst Area by paying the cost depicted in the Mirage effect, and they then activate their varying "During Set" effects. Any cards with Mirage can also be played normally.
"Mirage" is the fourth effect category after main, flash, and Burst effects. When an effect simply refers to a "set card", Mirage is included.
Once per turn during your Main Step, you can set down a card with Mirage face-up onto your Burst Area. This "once per turn" limit does not concern with the Burst, so you can set down both Burst and Mirage once each in the same turn. You cannot manually set down a card with Mirage from the Removed Zone. Furthermore, only one Mirage can be set at a time. You can also set a Mirage with effects, such as via Mirage Boost, ignoring the number of times You have set down a Mirage manually in the same turn.
While there is already a set Mirage, when you try to set a new Mirage, you switch places between the one that is already set and the new one after paying the cost for the new Mirage. You cannot simply return the set Mirage to hand without setting a new one. As swapping does not equate to increasing hand, any effects which trigger upon "increasing hand size" do not trigger when swapping Mirage.
The Burst Area can contain both a set Burst and a set Mirage at the same time. In this case, the Mirage and the Burst stack together, with the Mirage always above the Burst. When swapping the Mirage, the set Burst cannot be swapped together (the same applies if the Mirage is discarded). Vice versa, when discarding the set Burst, the set Mirage cannot be discarded together.
As the Burst Area is a separate zone to the field, any effects which reference or target the cards on the field cannot affect the Mirage. By the same logic, the Mirage itself also cannot activate its effects that does not have the "During Set" timing. You also cannot summon/deploy/use the set Mirage from the Burst Area. Also, Mirage cannot be affected unless the effect specifies "Mirage".
Like any other kind of effects, Mirage effects can be prevented by immunities.
Cards with Mirage