507. Beginning of Combat Step

In short

Beginn des Kampfes: Im Mehrspieler-Spiel wird der verteidigende Spieler festgelegt, dann Trigger und Priorität — die letzte Chance, eine Kreatur zu tappen oder zu entfernen, BEVOR Angreifer deklariert werden.

Informal summary — the official English text below is authoritative.

507.1.First, if the game being played is a multiplayer game in which the active player’s opponents don’t all automatically become defending players, the active player chooses one of their opponents. That player becomes the defending player. This turn-based action doesn’t use the stack. (See rule 506.2.)

507.2.Second, the active player gets priority. (See rule 117, “Timing and Priority.”)

Source: Wizards of the Coast, Magic: The Gathering Comprehensive Rules. Unofficial presentation under the Fan Content Policy. Rules effective as of Aug 7, 2026