Beginning of Upkeep

[adventus]

If my opponent has a {Call to the Grave} in play and the only creature I control is an {Etched Monstrosity}, can I untap, pay the mana, remove the counters and draw 3 cards before I sacrifice him?

[Keyeto]

No. The beginning of the upkeep is not an actual phase in which abilities can be activated. It's only purpose is for triggered abilities. Nothing else can be done at the BOU because nobody has priority.

Edit: Nevermind, I was incorrect. Corrected myself below.

[Fenster]

I think it goes "Untap, Upkeep, Draw"
So when his call triggers you can respond by doing that yes. You still have to sacrifice something in the end though but im thinking you know this.

[Fenster]

No. The beginning of the upkeep is not an actual phase in which abilities can be activated. It's only purpose is for triggered abilities. Nothing else can be done at the BOU because nobody has priority.

Doesnt priority happen once things trigger though?

[Keyeto]

No. The beginning of the upkeep is not an actual phase in which abilities can be activated. It's only purpose is for triggered abilities. Nothing else can be done at the BOU because nobody has priority.

Doesnt priority happen once things trigger though?

Yes, I actually misspoke. The abilities will go on the stack, and then you will be given priority to respond. You would have time to react.