Okay, my brother is running a game and has an artifact that taps artifacts in play. his opponent has an isochron scepter and has a lifegain spell imprinted on it. Now, opponent wants to use isochron during his upkeep. my brother wants to respond by using HIS artifact to tap isochron, and he is counting on the stack to tap opponent's artifact before isochron resolves.
so this creates a myriad of issues.
1. first of all, can any of this stuff even happen during the upkeep phase? I thought the upkeep was just the boardstate resetting before a player's turn began.
2. even if it can't and this happens during a turn, is this the proper use of the stack? because it doesn't seem like it should be to me.
3. and finally, if two dudes are about to use activated abilities at the same time, who gets priority? is it really just who announces first? if that's the case, then what if they announce at the same time?
1) The "reset" step is the untap step, no player gets priority here. Upkeep comes afterwards and is just like any other step/phase where players get priority, it is here, that the triggers for the beginning of the turn happen. Players get priority and can do stuff in response, or after something has resolved. The step ends only if all players pass priority in succession while the stack is empty, like any other such step/phase.
2) The opponent can use the Scepter when he gets priority during upkeep, yes. And while your brother can respond to that activation, doing so will not stop the Scepter's activation, since it gets tapped as a cost, so happens right when it is activated before anyone can respond. The Scepter is therefore already tapped, and its ability on the stack. There's no way for your brother to stop the Scepter with a tapping effect, it's either already too late, or the opponent can simply respond to that by activating the Scepter, which is not yet tapped.
3) This is exactly what priority is all about: It is the very right to do stuff. Only the player who has priority can do something. When a step/phase begins, the active player (the player whose turn it is) gets priority first. But even if that player uses it to cast a spell, activate an ability, or take a special action, unless it is something that doesn't use the stack (like most special actions, or mana abilities), the other players will always have the chance to respond before it actually happens (=resolves), because all players have to pass priority in succession for the top object on the stack to resolve.
so this creates a myriad of issues.
1. first of all, can any of this stuff even happen during the upkeep phase? I thought the upkeep was just the boardstate resetting before a player's turn began.
2. even if it can't and this happens during a turn, is this the proper use of the stack? because it doesn't seem like it should be to me.
3. and finally, if two dudes are about to use activated abilities at the same time, who gets priority? is it really just who announces first? if that's the case, then what if they announce at the same time?
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2) The opponent can use the Scepter when he gets priority during upkeep, yes. And while your brother can respond to that activation, doing so will not stop the Scepter's activation, since it gets tapped as a cost, so happens right when it is activated before anyone can respond. The Scepter is therefore already tapped, and its ability on the stack. There's no way for your brother to stop the Scepter with a tapping effect, it's either already too late, or the opponent can simply respond to that by activating the Scepter, which is not yet tapped.
3) This is exactly what priority is all about: It is the very right to do stuff. Only the player who has priority can do something. When a step/phase begins, the active player (the player whose turn it is) gets priority first. But even if that player uses it to cast a spell, activate an ability, or take a special action, unless it is something that doesn't use the stack (like most special actions, or mana abilities), the other players will always have the chance to respond before it actually happens (=resolves), because all players have to pass priority in succession for the top object on the stack to resolve.
Former Rules Advisor
"Everything's better with pirates." - Lodge
(The Gamers: Dorkness Rising)
"Any sufficiently analyzed magic is indistinguishable from science."
(Girl Genius - Fairy Tale Theater Break - Cinderella, end of volume 8)
Rule 503.1: The upkeep step has no turn-based actions. Once it begins, the active player gets priority.
RULES OF MAGIC :
http://magic.wizards.com/en/game-info/gameplay/rules-and-formats/rules