Cheapest priced copy (Wilds of Eldraine Promos): $0.49 at Card Kingdom, near mint, their price list as of .
Sentinel of Lost Lore 
Creature — Elf Knight · 3/4 · Rare · Wilds of Eldraine · #358
When this creature enters, choose one or more —
• Return target card you own in exile that has an Adventure to your hand.
• Put target card you don't own in exile that has an Adventure on the bottom of its owner's library.
• Exile target player's graveyard.
Legal inCommanderBrawlStandardPioneerModernLegacyVintage
Not legal inPauper
4 printings · $0.49 to $2.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Wilds of Eldraine Promos | 184p | Rare | $0.49 | $2.49 |
| Wilds of Eldraine Promos | 184s | Rare | — | $0.69 |
| Wilds of Eldraine | 184 | Rare | $0.49 | $0.49 |
| Wilds of Eldraine | 358 | Rare | $0.49 | $0.49 |
2 rulings from Wizards of the Coast
- 1 September 2023You must choose at least one mode if you can. If there are no legal targets available for the first two modes, you must choose the last mode. Notably, the last mode can target any player, even one who has no cards in their graveyard. In the unusual case there are no appropriate cards in exile to target and no player may legally be chosen as a target, the ability is removed from the stack with no effect.
- 1 September 2023The first and second modes of Sentinel of Lost Lore's ability can target any face-up exiled card that has an Adventure as long as it's owned by an appropriate player. It doesn't matter whether the card was cast as an Adventure.