Rules glossary
503.1 The upkeep step has no turn-based actions. Once it begins, the active player gets priority. (See rule 117, “Timing and Priority.”)
- 503.1a Any abilities that triggered during the untap step and any abilities that triggered at the beginning of the upkeep are put onto the stack before the active player gets priority; the order in which they triggered doesn’t matter. (See rule 603, “Handling Triggered Abilities.”) (refs: 603)