Nightmare Incursion — ruling 1

The cards are exiled face up, so everyone can see what they are. (This is true of every effect that exiles cards, unless the effect specifically says it exiles those cards face down.)

Nightmare Incursion : règles, fonctionnement et interactions (MTG)

Nightmare Incursion is one of those cards players keep asking about. Here is, in plain words, what its official text says, the rulings published by Wizards of the Coast, and the combos players actually run.

Official card text

Search target player's library for up to X cards, where X is the number of Swamps you control, and exile them. Then that player shuffles.

How it works : Nightmare Incursion

Original English text — Wizards of the Coast / Scryfall

#1August 1, 2008· Wizards of the Coast
The cards are exiled face up, so everyone can see what they are. (This is true of every effect that exiles cards, unless the effect specifically says it exiles those cards face down.)
No other card is named in this ruling.