Hamletback Goliath

Oracle Text

Whenever another creature enters the battlefield, you may put X +1/+1 counters on Hamletback Goliath, where X is that creature's power.

Card Rulings

7/1/2012 The value of X is determined as the ability begins resolving. If the other creature is no longer on the battlefield, its last known existence on the battlefield is checked to determine its power.