Cheapest priced copy (The List): $0.69 at Card Kingdom, near mint, their price list as of .
Curious Obsession 
Enchantment — Aura · Uncommon · Rivals of Ixalan · #35
Enchant creature
Enchanted creature gets +1/+1 and has "Whenever this creature deals combat damage to a player, you may draw a card."
At the beginning of your end step, if you didn't attack with a creature this turn, sacrifice this Aura.
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
3 printings · $0.69 to $1.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Jumpstart | 148 | Uncommon | $0.99 | — |
| The List | RIX-35 | Uncommon | $0.69 | — |
| Rivals of Ixalan | 35 | Uncommon | $0.79 | $1.99 |
One ruling from Wizards of the Coast
- 19 January 2018Curious Obsession's last ability is satisfied if any creature has attacked, similar to raid abilities. The creature it enchants doesn't have to have attacked.