Cheapest priced copy (Shadowmoor): $10.99 at Card Kingdom, near mint, their price list as of .
Helm of the Ghastlord 
Enchantment — Aura · Common · Shadowmoor · #166
Enchant creature
As long as enchanted creature is blue, it gets +1/+1 and has "Whenever this creature deals damage to an opponent, draw a card."
As long as enchanted creature is black, it gets +1/+1 and has "Whenever this creature deals damage to an opponent, that player discards a card."
Legal inCommanderModernLegacyVintagePauper
Not legal inBrawlStandardPioneer
2 printings · $10.99 to $94.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| The List | SHM-166 | Common | — | — |
| Shadowmoor | 166 | Common | $10.99 | $94.99 |
3 rulings from Wizards of the Coast
- 1 May 2008The two abilities trigger when the enchanted creature deals damage to an opponent of the creature’s controller, not when it deals damage to an opponent of the Helm’s controller. They trigger from any damage, not just combat damage.
- 1 May 2008If the enchanted creature is both of the listed colors, it will get both bonuses.
- 1 May 2008With regards to the two triggered abilities that Helm of the Ghastlord grants to the enchanted creature, the point when damage is actually dealt is the only time it matters what color the creature is. If the creature is blue or black at that time, the appropriate ability or abilities will trigger. They’ll resolve even if the creature changes color or loses its Aura.