Cheapest priced copy (Eldritch Moon): $1.49 at Card Kingdom, near mint, their price list as of .
Oath of Liliana 
Legendary Enchantment · Rare · Eldritch Moon · #99
When Oath of Liliana enters, each opponent sacrifices a creature of their choice.
At the beginning of each end step, if a planeswalker entered the battlefield under your control this turn, create a 2/2 black Zombie creature token.
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
2 printings · $1.49 to $6.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Eldritch Moon | 99 | Rare | $1.49 | $3.49 |
| Eldritch Moon Promos | 99s | Rare | — | $6.99 |
3 rulings from Wizards of the Coast
- 13 July 2016The last ability triggers only once per turn, even if more than one planeswalker entered the battlefield under your control.
- 13 July 2016Oath of Liliana is legendary, just like the previous Oaths from Oath of the Gatewatch. If you already control an Oath of Liliana, you can still cast a second Oath of Liliana to take advantage of its enters-the-battlefield ability. It will enter the battlefield, causing its first ability to trigger. You will then choose one to keep, and the other will be put into your graveyard.
- 13 July 2016Oath of Liliana’s last ability will trigger even if the planeswalker that entered the battlefield under your control is no longer on the battlefield, no longer under your control, or no longer a planeswalker. This is also true if Oath of Liliana wasn’t on the battlefield when the planeswalker entered.