Bifur, Melodic Rider (HOB-147) - The Hobbit

Storied (If you control three or more artifacts, legendaries, andlor 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 an ability of a Dwarf you control triggers, that ability triggers an additional time.