At the beginning of your upkeep, you may put a fuse counter on this artifact.

, Sacrifice this artifact: Destroy each artifact and creature with mana value equal to the number of fuse counters on this artifact.
Putting on a counter is optional. If you forget, you can’t go back later even if it is something you usually do.
Only destroys artifacts and creatures with exactly the specified cost. It does not mean “less than or equal to”.