Roger's Egg

When Roger's Egg enters the battlefield or
becomes tapped, put a Journey counter on it.
{t}: Add {1} to your mana pool, if there are three
or more Journey counters on Roger's Egg create
two treasure tokens instead. If there are seven or
more counters put a 15/15 Red and Green
legendary dragon, named Uranus, with flying,
trample. and indestructible onto the battlefield,
then sacrifice Roger's Egg.