Do you have to choose and/or reveal the creature when Aether Vial's ability is placed on the stack or when the vials ability resolves? So if my opponent responds to vial being activated can I then change my decision on what creature to vial in after their response resolves assuming my vial trigger remains on the stack?
First time posting here so let me know what I can add to make my question better.
The creature entering the battlefield is the resolution of Vial’s activated ability. Your opponent can respond to you tapping Vial and putting the ability on the stack but they don’t get any knowledge of what you might put onto the battlefield. So yes you can certainly change your mind from what you had intended to put on the field if your opponent takes an action that changes your mind either way your opponent won’t know whether or not you changed your mind or not. Also, once the creature enters its etb abilities trigger right away. It’s also important to know that your opponent doesn’t get the chance to affect your choice of copy for cards like Phantasmal Image since it enters as a copy it’s not a trigger.
First time posting here so let me know what I can add to make my question better.
Thank you,