Atarka Pummeler
Creature — Ogre Warrior
Formidable — 
: Creatures you control gain menace until end of turn. Activate only if creatures you control have total power 8 or greater. (They can't be blocked except by two or more creatures.)
Lucas Graciano
Dragons of Tarkir (DTK)
• #129Rulings
If you control a creature with power less than 0, use its actual power when calculating the total power of creatures you control. For example, if you control three creatures with powers 4, 5, and -2, the total power of creatures you control is 7.
(wotc • 2015-02-25)
Some formidable abilities are activated abilities that require creatures you control to have total power 8 or greater. Once you activate these abilities, it doesn’t matter what happens to the total power of creatures you control.
(wotc • 2015-02-25)
Activating Atarka Pummeler’s ability more than once conveys no additional benefit to creatures you control.
(wotc • 2015-02-25)
Other formidable abilities are triggered abilities with an “intervening ‘if’” clause. Such abilities check the total power of creatures you control twice: once at the appropriate time to see if the ability will trigger, and again as the ability tries to resolve. If, at that time, the total power of creatures you control is no longer 8 or greater, the ability will have no effect.
(wotc • 2015-02-25)
Rulings
If you control a creature with power less than 0, use its actual power when calculating the total power of creatures you control. For example, if you control three creatures with powers 4, 5, and -2, the total power of creatures you control is 7.
(wotc • 2015-02-25)
Some formidable abilities are activated abilities that require creatures you control to have total power 8 or greater. Once you activate these abilities, it doesn’t matter what happens to the total power of creatures you control.
(wotc • 2015-02-25)
Activating Atarka Pummeler’s ability more than once conveys no additional benefit to creatures you control.
(wotc • 2015-02-25)
Other formidable abilities are triggered abilities with an “intervening ‘if’” clause. Such abilities check the total power of creatures you control twice: once at the appropriate time to see if the ability will trigger, and again as the ability tries to resolve. If, at that time, the total power of creatures you control is no longer 8 or greater, the ability will have no effect.
(wotc • 2015-02-25)