Unstable Monster

Unstable Monsters (Japanese: Fuantei Monsutā) are a Type of  that has a tan colored card frame.

Characteristics
They start the Duel in the Extra Deck:


 * They cannot exist in the hand or the Main Deck; if an Unstable Monster would be moved to the hand or Main Deck, it is returned to the Extra Deck instead.
 * If an Unstable Monster is not properly Special Summoned by Unstable Summon before being sent to the Graveyard or banished, it cannot be Special Summoned from there (even by effects that ignore Summoning conditions).

Unstable Materials
Unstable Materials are the requisite monsters needed to Unstable Summon the Unstable Monster. Each Unstable Monster lists its required Unstable Materials in the first line of its card text.

Unstable Summoning
In order to perform an Unstable Summon, the requisite Unstable Materials must be currently marked for destruction. At this point, you can instead banish those monsters and Special Summon an Unstable Monster that lists a combination of the monsters that would've been destroyed. This Summon is performed immediately at the resolution of the chain, and it does not form a chain itself.

Instability
All Unstable Monsters share some variation of the following effect:

During the third End Phase after this card was Summoned: Return it to your Extra Deck, and if you do, return the monsters banished to Special Summon this card to the field (This effect cannot be negated.)