Bifur, Melodic Rider

Storied (If you control three or more artifacts, legendaries, and/or Sagas, you have an enduring story for the rest of the game.)

Whenever Bifur enters or attacks, put a +1/+1 counter on target creature.

As long as you have an enduring story, if a triggered ability of a Dwarf you control triggers, that ability triggers an additional time.