Armory

Equipped creature has +1/+1
When Armory comes into play put 3 decay counters on it. Remove 1 decay counter at the start of your upkeep, then sacrifice this artifact if there are no decay counters on it. When you level up this card reset the decay counters to 3.
Level up {3} ({3}:Put a level counter on this. Level up only as a sorcery.)
Level 2-3 : Equipped creature has +2/+2
Level 4+ : Equipped creature has +3/+3
Equip {2}({2}: Attach to target creature you control. Equip only as a sorcery.