Viridian Corrupter
Creature — Phyrexian Elf Shaman
Infect (This creature deals damage to creatures in the form of -1/-1 counters and to players in the form of poison counters.)
When Viridian Corrupter enters, destroy target artifact.
Matt Cavotta
Mirrodin Besieged (MBS)
• #94Rulings
If there are no artifacts on the battlefield when Viridian Corrupter enters the battlefield, its enters-the-battlefield does nothing. Viridian Corrupter will simply enter the battlefield.
(wotc • 2011-06-01)
The enters-the-battlefield ability is not optional. You must target an artifact you control if there are no other artifacts on the battlefield.
(wotc • 2011-06-01)
Rulings
If there are no artifacts on the battlefield when Viridian Corrupter enters the battlefield, its enters-the-battlefield does nothing. Viridian Corrupter will simply enter the battlefield.
(wotc • 2011-06-01)
The enters-the-battlefield ability is not optional. You must target an artifact you control if there are no other artifacts on the battlefield.
(wotc • 2011-06-01)