Cheapest priced copy (Nemesis): $0.35 at Card Kingdom, near mint, their price list as of .
Laccolith Rig 
Enchantment — Aura · Common · Nemesis · #88
Enchant creature
Whenever enchanted creature becomes blocked, you may have it deal damage equal to its power to target creature. If you do, the first creature assigns no combat damage this turn.
Legal inCommanderLegacyVintagePauper
Not legal inBrawlStandardPioneerModern
1 printing · $0.35 to $1.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Nemesis | 88 | Common | $0.35 | $1.99 |
7 rulings from Wizards of the Coast
- 4 October 2004The ability is optional. You can decide to allow it to deal combat damage as normal.
- 4 October 2004The ability allows you to deal damage during the declare blockers step of combat, which is well before even first strike creatures deal damage.
- 4 October 2004It can target any creature on the battlefield, not just one of the ones blocking it.
- 4 October 2004If placed on a Laccolith creature, both this card’s ability and the Laccolith’s ability will trigger and have their effect.
- 4 October 2004The ability triggers even if a spell or ability makes it blocked, instead of being blocked by a creature.
- 4 October 2004If this is on an opponent’s creature, the controller of this card (not the creature’s controller) decides whether to use this card’s ability or not, and decides what the target will be.
- 15 October 2006Moving the enchantment after the ability triggers will not affect which creatures are affected.