Zealot il-Vec

Oracle Text

Shadow (This creature can block or be blocked by only creatures with shadow.)

Whenever Zealot il-Vec attacks and isn't blocked, you may have it deal 1 damage to target creature. If you do, prevent all combat damage Zealot il-Vec would deal this turn.

Card Rulings

9/25/2006 When Zealot il-Vec attacks and isn’t blocked, you must choose a target for its ability even if you don’t use it.
9/25/2006 If you choose to have Zealot il-Vec deal 1 damage to a creature and that damage is prevented or replaced, Zealot il-Vec’s combat damage will still be prevented.
4/15/2013 An ability that triggers when something “attacks and isn’t blocked” triggers in the declare blockers step after blockers are declared if (1) that creature is attacking and (2) no creatures are declared to block it. It will trigger even if that creature was put onto the battlefield attacking rather than having been declared as an attacker in the declare attackers step.