Damage from spells, abilities or combat damage that is not lethal will remain marked on a creature until the cleanup step at the end of each turn. Creatures can be dealt damage and remain on the battlefield until it is dealt additional damage, or until its toughness is reduced such that the damage marked on it is now lethal. In these instances, the creature will end up going to the graveyard.

Scourge of Geier Reach gets +1/+1 for each creature controlled by an opponent. This ability continually checks the total bonus given to the Scourge as the number of creatures controlled by your opponent(s) changes. The fact that damage remains marked on creatures until the cleanup step matters when dealing with the Scourge.

For example, if Scourge of Geier Reach blocks an Unholy Fiend, and that is the only creature that your opponent controls, then in the end, both of these creatures will go to the graveyard. After combat damage is dealt, state-based actions are checked and the Unholy Fiend will be destroyed, since it has four damage marked on it. Then, because a state-based action was performed, they are checked again. At this point, the Scourge will be a 3/3 with three points of damage on it, and it too will be destroyed.

Let’s use the same example, only this time your opponent also controls a Silverchase Fox. In this situation, the Scourge will not die immediately after combat damage has been dealt. However, after combat damage has been dealt, if your opponent sacrifices the Fox to destroy an enchantment, the Scourge will be destroyed at that point since its toughness is now three and it has three damaged marked on it.