Cheapest priced copy (Planar Chaos): $4.99 at Card Kingdom, near mint, their price list as of .
Keen Sense 
Enchantment — Aura · Uncommon · Time Spiral Remastered · #213
Enchant creature
Whenever enchanted creature deals damage to an opponent, you may draw a card.
Legal inCommanderModernLegacyVintage
Not legal inBrawlStandardPioneerPauper
3 printings · $4.99 to $99.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Planar Chaos | 152 | Uncommon | $4.99 | $99.99 |
| The List | PLC-152 | Uncommon | $4.99 | — |
| Time Spiral Remastered | 213 | Uncommon | $4.99 | $27.99Out of stock |
2 rulings from Wizards of the Coast
- 16 March 2018You draw one card each time the enchanted creature deals damage to an opponent, no matter how much damage it deals or whether it was dealt in combat.
- 16 March 2018If this Aura enchants an opponent's creature, you won't draw a card when that creature damages you. The creature has to deal damage to one of your opponents for the ability to trigger.