Thought Erasure
Sorcery
Target opponent reveals their hand. You choose a nonland card from it. That player discards that card.
Surveil 1. (Look at the top card of your library. You may put it into your graveyard.)
"It's truly the highest honor, isn't it? To be remembered? Pity for you."
Anna Steinbauer
Guilds of Ravnica (GRN)
• #206Rulings
Some spells that instruct you to surveil require targets. You can't cast a spell without choosing legal targets. If all of those targets become illegal, the spell doesn't resolve and you won't surveil.
(wotc • 2024-01-12)
You perform the actions stated on a card in sequence. For some spells and abilities, you'll surveil last. For others, you'll surveil and then perform other actions.
(wotc • 2024-01-12)
You surveil 1 even if the opponent doesn't discard a card, perhaps because they had no cards in hand at all.
(wotc • 2018-10-05)
Rulings
Some spells that instruct you to surveil require targets. You can't cast a spell without choosing legal targets. If all of those targets become illegal, the spell doesn't resolve and you won't surveil.
(wotc • 2024-01-12)
You perform the actions stated on a card in sequence. For some spells and abilities, you'll surveil last. For others, you'll surveil and then perform other actions.
(wotc • 2024-01-12)
You surveil 1 even if the opponent doesn't discard a card, perhaps because they had no cards in hand at all.
(wotc • 2018-10-05)