Aspect of Earth

When Aspect of Earth enters the battlefield, creatures you control get +1/+2 and "{1}: add one mana of any color to your mana pool"
During cleanup of end phase, this enchantment goes to exile
If this card is countered, shuffled into library, milled, put into graveyard from anywhere, put it in exile instead
If this card is milled, put it in exile, then, if your commander is Arex, Aspect of Elements, this aspect costs {g} less to cast from Exile