Blood Operative

Lifelink
When this creature enters, you may exile target card from a graveyard.
Whenever you surveil, if this card is in your graveyard, you may pay 3 life. If you do, return this card to your hand.

Guilds of Ravnica Promos

Guilds of Ravnica

Lifelink
When Blood Operative enters the battlefield, you may exile target card from a graveyard.
Whenever you surveil, if Blood Operative is in your graveyard, you may pay 3 life. If you do, return Blood Operative to your hand.

If you surveil and put Blood Operative into your graveyard as you do so, its ability triggers once you've finished surveilling.

No player may take actions between the time you choose to pay 3 life and the time you return Blood Operative to your hand.

An ability that triggers "whenever you surveil" triggers after you're done surveilling, even if you have fewer cards in your library than the number of cards you're instructed to surveil. It even triggers if you have no cards in your library.