Wall of Mourning — ruling 1

You don't get to look at the cards exiled with Wall of Mourning. If there are more than one, you choose which one to put back into your hand at random without looking at them. This is true even if you knew what one or more cards from the top of your library were before exiling them.

Wall of Mourning : règles, fonctionnement et interactions (MTG)

Wall of Mourning 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

Defender When this creature enters, exile a card from the top of your library face down for each opponent you have. Coven — At the beginning of your end step, if you control three or more creatures with different powers, put a card exiled with this creature into its owner's hand.

How it works : Wall of Mourning

Original English text — Wizards of the Coast / Scryfall

#1September 24, 2021· Wizards of the Coast
You don't get to look at the cards exiled with Wall of Mourning. If there are more than one, you choose which one to put back into your hand at random without looking at them. This is true even if you knew what one or more cards from the top of your library were before exiling them.
No other card is named in this ruling.