City of Shadows
Land
, Exile a creature you control: Put a storage counter on City of Shadows.
: Add
for each storage counter on City of Shadows.
Illustrated by
Legality
Rulings
Oct 4, 2004
The storage counters aren’t removed when you activate the mana ability.
Oct 1, 2009
You can activate City of Shadows’s second ability while it has no storage counters on it, though it won’t add any mana to your mana pool in this case. You did not tap it for mana, though, in case any abilities (such as the ability of a Fertile Ground enchanting it) care about that.
