Each card in this deck is a metallic plate, each adorned with a distinct portrait of its own. The card shimmers with power, and while each Deck of Many Things is different, all legends agree that this kind of artifact holds great power and is not to be used lightly. The exact contents and powers of the deck cannot be known unless the cards are drawn...but once drawn, the effect on the user is irreversible. Supposedly, a Deck of Many Things can only be used so many times until it disappears and moves elsewhere in the multiverse...for what reason, no-one knows.
AD&D 3.5 DM's Guide "Deck of Many Things"
A deck of many things (both beneficial and baneful) is usually found in a box or leather pouch. Each deck contains a number of cards of plaques made of ivory of vellum. Each is engraved with glyphs, characters, and sigils. As soon as one of hese cards is drawn from the pack, its magic is bestowed upon the person who drew it, for better or worse.
The character with a deck of many things who wishes to draw a card must announce how many cards she will draw before she begins. Cards must be drawn within 1 hour of each other, and a character can never again draw from this deck any more cards than she has announced. If the character does not willingly draw her allotted number (or if she is somehow prevented from doing so), the cards flip out of the deck on their own. Exception: if the jester is drawn, the possessor of the deck may elect to draw two additional cards.
Each time a card is taken from the deck, it is replaced (making it possible to draw the same card twice) unless the draw is the jester or the fool, in which case the car is discarded from the pack. A deck of many things contains 22 cards. To simulate the magic cards, you may want to use tarot cards, as indicated in the second column of the accompanying table. If no tarot deck is available, substitute ordinary playing cards instead, as indicated in the third column. The effects of each card, summarized on the table, are fully described below.
Balance: Change alignment instantly.
Comet: Defeat the next monster you meet to gain one livel.
Donjon: You are imprisoned. (Trapped in an extra-dimensional pocket.)
Euryale: -1 penalty on all saving throws henceforth.
The Fates: Avoid any situation you choose...once.
Flames: Enmity between you and an outsider.
Fool: Lose 10,000 experience points and you must draw again.
Gem: Gain your choice of 25 pieces of jewelry of 50 gems.
Idiot: Lose Intelligence (permanent drain). You may draw again.
Jester: Gain 10,000 XP or two more draws from the deck.
Key: Gain a major magic weapon.
Knight: Gain the service of a 4th-level fighter.
Moon: You are granted 1d4 wishes.
Rogue: One of your friends turns against you.
Ruin: Immediately ose all wealth and real property.
Skull: Defeat dread wraith or be forever destroyed.
Star: Immediately gain a +2 inherent bonus to one ability score.
Sun: Gain beneficial medium wondrous item and 50,000 XP.
Talons: All magic items you possess disappear permanently.
Throne: Gain a +6 bonus on diplomacy checks plus a small keep.
Vixier: Know the answer to your next dilemma.
The Void: Body functions, but soul is trapped elsewhere.
Balance: As in "weighed in the balance and found wanting," the character must change to a radically different alignment. If the character fails to act according to the new alignment, she gains a negative level.
Comet: The character must single-handedly defeat the next hostile monster or monsters encountered, or the benefit is lost. If successful, the character gains enough XP to attain the next experience level.
Donjon: This card signifies imprisonment--either by the imprisonment spell or by some powerful being, at the DM's option. All gear and spells are stripped from the victim in any case. Whether these items are recoverable is, likewise, up to the DM. Draw no more cards.
Euryale: The medusalike visage of this card brings a curse that only the fates card or a deity can remove. The -1 penalty on all saving throws is otherwise permanent.
Fates: This card enables the character to avoid even an instantaneous occurrence if so desired, for the fabric of reality is unraveled and respun. Note that it does not enable something to happen. It can only stop something from happening or reverse a past occurrence. The reversal is only for the character who drew the card; other party members may have to endure the situation.
Flames: Hot anger, jealousy, and envy are but a few of the possible motivational forces for the enmity. The enmity of the outsider can't be ended until one of the parties has been slain. Determine the outsider randomly, and assume that it attacks the character (or plagues her life in some way) within 1d20 days.
Fool: The payment of XP and the redraw are mandatory. This card is always discarded when drawn, unlike all others except the jester.
Gem: This card indicates wealth. The jewelry is all gold set with gems, each piece worth 2,000 gp, the gems 1,000 gp value each.
Idiot: This card causes the drain of 1d4+1 points of Intelligence immediately. The additinal draw is optional.
Jester: This card is always discarded when drawn, unlike all others except the fool. The redraws are option.
Key: The magic weapon granted must be one usable by the character; use the weapon tables beginning with Tabe 7-10: Weapon Type Determination until a useful item is awarded. It suddenly appears out of nowhere in the character's hand.
Knight: The fighter appears out of nowhere and serves loyally until death. He or she is of the same race (or kind) and gender as the character (See Chapter 4 of this book for typical NPC statistics for a 4th-level fighter.)
Moon: This card sometimes bears the image of a moonstone gem with the appropriate number of wishes shown as gleams therein; sometimes it depicts a moon with its phase indicating the number of wishes (full=4; gibbous=3; half=2; quarter=1). These wishes are the same as those granted by the 9th-level wizardd spell and must be used within a number of minutes equal to the number received.
Rogue: When this card is drawn, one of the character's NPC friends (preferably a cohort) is totally alienated and forever after hostile. If the character has no cohorts, the enmity of some powerful personage (or community, or religious order) can be substituted. The hatred is secret until the time is ripe for it to be revealed with devastating effect.
Ruin: As implied by its name, when this card is drawn, all non-magical possessions of the drawer are lost.
Skull: A dread wraith (see page 258 of the Monster Manual) appears. Treat this creature as an unturnable undead. The character must fight it alone--if others help, they get dread wraiths to fight as well. If the character is slain, she is slain forever and cannot be revived, even with a wish or a miracle.
Star: The 2 points are added to any ability the character chooses. They cannot be divided among 2 abilities.
Sun: Roll for a medium wondrous item (Table 7-28: Medium Wondrous Items) until a useful item is indicated.
Talons: When this card is drawn, every magic item owned or possessed by the character is instantly or irrevocably gone.
Throne: The character becomes a true leader in people's eyes. The castle gained appears in any open area she wishes (but the decision where to place it must be made within 1 hour).
Vizier: This card empowers the character drawing it with the one-time ability to call upon a source of wisdom to solve any single problem or answer fully any question upon her request. The query must be made within one year. Whether the information gained can be successfully acted upon is another question entirely.
The Void: This black card spells instant disaster. The character's body continues to function, as though comatose, but her psyche is trapped in a prison somewhere--in an object on a far plane or planet, possibly in the posession of an outsider. A wish or a miracle does not bring the cahracter back, instead merely revealing the plane of entrapment. Draw no more cards.
Essentially, the Deck of Many Things is the Jemanji of D&D, except that in Jemanji you roll because you have to finish the game before this stuff kills you, and with the Deck of Many Things, you're just...drawing cards because you're a gambling risk-taker. In BG2/ToB, Abdel and a demon gamble against each other, the idea being that each would draw three cards, suffer through the effects, and the person who got the better cards wins.
My thought: "each Deck of Many Things is different," so it might be fun to do a post with a crack version--people participating make up their own cards and effects, which will be confined to the post/however long they want, through the magic of CAMP SPACE/TIME WARP because the Deck canonically screws with the very fabric of reality anyway. XD
A person might draw a card and be thrown into a CRAB BATTLE, or another person might draw a card and get a small snow fort, etc.
So. Those who read this journal: good idea, annoying and bad idea, Imoen just go jump off a cliff?