When your opponent passes priority during his end step you may activate Adarkar Valkyrie's ability targeting Angel of Despair. When that ability resolves your opponent will be given priority. When he passes priority again you may activate High Market sacrificing Angel of Despair.
Remember: all players must pass priority in succession for a spell or ability to resolve or for a step or phase to end.
I think I misread Adarkar Valkyrie. Can I target Angel of Despair before activating High Market?
Since you have the proper order here to accomplish what you want, yes, that works fine. A step or phase only ends if both players pass priority without taking any actions AND the stack is empty.
If you activate Adarkar Valkyrie's ability, targeting Angel of Despair, then both players will have the opportunity to cast spells and/or activate abilities after that ability resolves. Your opponent gets priority after Adarkar Valkyrie's abaility resolves, but if passes in his end step, you will get priority and have an opportunity to activate High Market's ability.
It is my opponent's turn. He passes priority on his End Step. I want to accomplish the following:
1) Activate High Market to sacrifice Angel of Despair.
2) Activate Adarkar Valkyrie to return Angel of Despair to the battlefield
Do I still have priority after #1 resolves to accomplish #2? My gut feeling is no, since I am not the active player.
EDIT: I think I misread Adarkar Valkyrie. Can I target Angel of Despair before activating High Market?
Remember: all players must pass priority in succession for a spell or ability to resolve or for a step or phase to end.
[card=Jace Beleren]Jace[/card] = Jace
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The first rule of Cursecatcher is, You do not talk about Cursecatcher.
Since you have the proper order here to accomplish what you want, yes, that works fine. A step or phase only ends if both players pass priority without taking any actions AND the stack is empty.
If you activate Adarkar Valkyrie's ability, targeting Angel of Despair, then both players will have the opportunity to cast spells and/or activate abilities after that ability resolves. Your opponent gets priority after Adarkar Valkyrie's abaility resolves, but if passes in his end step, you will get priority and have an opportunity to activate High Market's ability.