MTG Keyword Rules — Comprehensive Rules Glossary

Epic represents two spell abilities, one of which creates a delayed triggered ability. “Epic” means “For the rest of the game, you can’t cast spells,” and “At the beginning of each of your upkeeps for the rest of the game, copy this spell except for its epic ability. If the spell has any targets, you may choose new targets for the copy.” See rule 707.10.

A player can’t cast spells once a spell with epic they control resolves, but effects (such as the epic ability itself) can still put copies of spells onto the stack.