Risen Executioner
Creature — Zombie Warrior
This creature can't block.
Other Zombie creatures you control get +1/+1.
You may cast this creature from your graveyard if you pay 
more to cast it for each other creature card in your graveyard.
Craig J Spearing
Dragons of Tarkir (DTK)
• #116Rulings
Once you start to cast Risen Executioner from your graveyard, you’ll finish casting it, including paying its cost, before any player receives priority. No one can respond in time to affect the cost you’ll pay (perhaps by destroying one of your other creatures).
(wotc • 2015-02-25)
Risen Executioner’s last ability doesn’t change when you can cast it.
(wotc • 2015-02-25)
Rulings
Once you start to cast Risen Executioner from your graveyard, you’ll finish casting it, including paying its cost, before any player receives priority. No one can respond in time to affect the cost you’ll pay (perhaps by destroying one of your other creatures).
(wotc • 2015-02-25)
Risen Executioner’s last ability doesn’t change when you can cast it.
(wotc • 2015-02-25)