Upkeep step

From MTG Salvation Wiki

Turn Structure
Beginning Phase
Untap Step
Upkeep Step
Draw Step
Main Phase
Combat Phase
Beginning of Combat Step
Declare Attackers Step
Declare Blockers Step
Combat Damage Step
End of Combat Step
Main Phase
End Phase
End of Turn Step
Cleanup Step

The upkeep step is the second step of the beginning phase. It is the first time during a turn when players gain priority.

At the beginning of the upkeep step, any abilities that trigger either during the untap step or at the beginning of upkeep go on the stack. Then the active player gains priority.

From the Comprehensive Rules 303. Upkeep Step 303.1. As the upkeep step begins, any abilities that trigger at the beginning of that upkeep step and any abilities that triggered during the turn’s untap step go on the stack. (See rule 410, “Handling Triggered Abilities.”) Then the active player gets priority and players may play spells and abilities.