Sentinel of Lost Lore

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.

Wilds of Eldraine Promos

Wilds of Eldraine

When Sentinel of Lost Lore enters the battlefield, 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.

The 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.

You 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.