Epic

Epic is a keyword ability that changes the rules for playing spells for the player that plays the epic spell. When an epic spell resolves, it prevents the player who played it from playing anymore spells for the rest of that game. The keyword was introduced in Betrayers of Kamigawa and has appeared on the following five spells: Endless Swarm, Enduring Ideal, Eternal Dominion, Neverending Torment and Undying Flames.

From the Comprehensive Rules:

• 502.44. Epic
  • 502.44a Epic represents both a static ability and a delayed triggered ability. "Epic" means, "For the rest of the game, you can’t play spells," and “At the beginning of each of your upkeeps, copy this spell except for its epic ability. If the spell has any targets, you may choose new targets for the copy.” See rule 503.10.
  • 502.44b A player can’t play spells once a spell with epic he or she controls resolves, but effects (such as the epic ability itself) can still put copies of spells onto the stack.

For your reference [CR 503.10]:

• 503.10. To copy a spell means to put a copy of the spell onto the stack; a copy of a spell isn’t "played." In addition to copying the characteristics of the spell, all decisions made when the spell was played are copied. These include mode, targets, the value of X, and optional additional costs such as buyback. (See rule 409, "Playing Spells and Activated Abilities.") Choices that are normally made on resolution are not copied. If an effect of the copy refers to objects used to pay its costs, it uses the objects used to pay the costs of the original spell. A copy of a spell is controlled by the player who put it on the stack. A copy of a spell is itself a spell, but it has no spell card associated with it. It works just like a normal spell: it can be countered or it can resolve, and it uses the same timing rules as normal spells.
  • Example
    A player plays Fork, targeting an Emerald Charm. Fork reads, "Put a copy of target instant or sorcery spell onto the stack, except that it copies Fork’s color and you may choose new targets for the copy." Emerald Charm reads, "Choose one — Untap target permanent; or destroy target non-Aura enchantment; or target creature loses flying until end of turn." When the Fork resolves, it puts a copy of the Emerald Charm on the stack. The copy has the same mode that was chosen for the original Emerald Charm. It does not necessarily have the same target, but only because Fork allows choosing of new targets.
  • Example
    Fling is an instant that reads, "As an additional cost to play Fling, sacrifice a creature." Fling deals damage equal to the sacrificed creature’s power to target creature or player.” When determining how much damage a copy of Fling deals, it checks the power of the creature sacrificed to pay for the original Fling.
  • 503.10a A copy of a spell in a zone other than the stack ceases to exist. A copy of a card in any zone other than the stack or the in-play zone ceases to exist. This is a state-based effect. See rule 420.

Further references may be found in the Comprehensive Rules.