Dragon Essence Goblet.

Each time a Dragon leaves the battlefield to go to
the graveyard, put a +1/+1 counter on Dragon
Essence Goblet.
Whenever a Dragon enters the battlefield under
your control, transfer all counters on this artifact
to it.
—
A dragon, my dear, doesn't really die. It's energy
remains forever.
—Thoa 'ndun, shepherdess of dragons.