Ore-Touched Prospector

When Ore-Touched Prospector enters the battlefield, put a gravity counter on it.

As long as Ore-Touched Prospector has 2 or more gravity counters, it has {t}{g}

As long as it has 4 or more gravity counters, it has {t}{b}{g}

As long as it has 8 or more gravity counters, it has {t}: Add three mana of any one color.