Obsidiax, the Earthbreaker

When Obsidiax, the Earthbreaker enters the battlefield, create a number of colorless artifact
tokens named Unstable Obelisk with "{t}: Add {c}." and "{7}, {t}, Sacrifice Unstable Obelisk:
Destroy target permanent." equal to the number
of basic land types among lands you control.
You may pay {1} rather than pay the activation
cost of the first artifact ability you activate during
each of your turns.