Mental Magic

Mental Magic is a limited Magic: The Gathering format in which a card can be played as any card in the game with the same exact mana cost. 
==Description==
All you need is an opponent and a stack of nonland cards to form both of your decks. Players start with seven-card hands, just like in a regular game of Magic, but all players draw from the same library of cards. 
Cards may be played in one of two ways:
1. Any card may be played face down as a "Utopia," a basic land that's capable of producing any color of mana. Although these lands are basic, they have no subtypes (they're not Swamps, for example). Note that players may still play only one land on each of their turns.
2. A card may be played as any card in Magic with the same mana cost as that card — except for the card it actually is! In order to "mentally" play a card, a player must be able to accurately describe its card text with no outside help.
Once a card has been named, that card can't be named again for the rest of the game. In fact, if a card is returned to your hand and you want to play it again, you can't name the card you named before. You have to choose a different card with that mana cost.
There are some additional Mental Magic rules that you can play with or not as your group sees fit. Cards in your hand, graveyard, or anywhere else other than in play have no names — but they do have types and subtypes. If you play <c>Raise Dead</c> or <c>Duress</c>, for example, read what's actually printed on the card. Also, library-searching effects don't work. If you play a spell or ability that tells you to search your library, that part of the effect doesn't do anything (As if there's a <c>Mindlock Orb</c> in play).
Mental Magic challenges players' knowledge of Magic and allows for a quick, fun way to pass the time between matches. 
===Examples===
* A card can be played as <c>Ray of Command</c>, <c>Phantasmal Forces</c>, or simply as a rainbow land!
* <c>Fugitive Wizard</c> (which has a mana cost of ) could be played as <c>Cursecatcher</c>, <c>Unsummon</c> or <c>Ancestral Recall</c>, but couldn't be played as Fugitive Wizard. 
* <c>Scathe Zombies</c> can be used as <c>Unhinge</c>, <c>Stinkweed Imp</c>, <c>Looming Shade</c>, or even <c>Yawgmoth's Will</c>
==Reverse Mental Magic==
The rules in Reverse Mental Magic are the same as Mental Magic with a single twist: your opponent gets to name the card you're playing! Players still draw from the same communal deck of nonland cards, they can still play cards in their hand face down as lands that produce any color of mana, and cards still can't be played as themselves.
The difference is that you don't know what spell you're playing when you play it. For example, if you've got a card in your hand, you'll tap three lands, show the card to your opponent, and then your opponent tries to think of the least scary card with that mana cost and name it. Players can't help but enjoy themselves as they watch their opponents struggle to name weak cards, only to eventually run out of options and provide their enemy with something to do them in. Reverse Mental Magic is a great alternative for those players already well versed in regular Mental Magic play.
==Notes==
* As the format is unsanctioned and definitively casual, exact rules change from group to group groups must decide on their own banned lists, on whether Utopias count as "<c>Plains</c>-<c>Island</c>-<c>Swamp</c>-<c>Mountain</c>-<c>Forest</c>"'s, etc. 
* <c>Richard Garfield, Ph.D.</c>, a card from the Unhinged un-set, allows its controller (only) to play as though they were in a match of Mental Magic. This references Garfield's hand in the creation and development of Mental Magic.
* If building a stack, it may be useful to include hybrid cards. The rules must be clarified that hybrids function as any possible cost between them, but this can help out the mana costs that tend to end up being named the same thing (e.g. ) without just removing the cards.
* Lands may be played as any nonbasic (or basic) land.
==References==