The Deck of Many Things
This information applies to all PCs entering combat with a card or cards from The Deck on their person:
Card effects manifest automatically at the start of any combat encounter where at least one card is present. Only one card can be manifest at any given time. When a combat encounter begins and more than one card is present, the manifesting card will be determined randomly from among the cards present.
An environmental effect (token) representing a card’s manifestation will appear in a random square adjacent to the character in possession of the card. In order to activate the power of a card, at least one square of a creature’s space must occupy the token’s square. Encounter powers derived from card tokens may only be used once per encounter, often with a lingering effect on or near the tokens original location. At-will powers generally remain for the duration of the encounter and may be used multiple times.
A creature holding a card can attempt to force that card’s effect to manifest, replacing the effect of another card, such as one that manifested at the start of the encounter. The creature makes a DC 18 Arcana check as a minor action. If the check is successful, the previous environmental effect ends, its token is removed from play, and the new effect begins. The user of the card can place the new token in a square adjacent to that creature or in the creature’s square (granting immediate access to the card’s power). The new effect likewise persists until the end of the encounter, unless it is replaced.
See individual card descriptions for details of their effects: