Death Strike

When Death Strike enters the battlefeild, put X time counters on enchanted creature.
At the beggining of your upkeep, remove a time counter from enchanted creature.
When there are no time counters on enchanted creature, sacrifice it.
Enchanted creature has +2/+2
If enchanted creature is black or green, it gets an additional +1/+1
If enchanted creature is black and green, it gets an additional +2/+1 instead