Anowon, the Ruin Thief — ruling 1

Because damage remains marked on a creature until the damage is removed as the turn ends, nonlethal damage dealt to other Rogues you control may become lethal if Anowon leaves the battlefield during that turn.

Anowon, the Ruin Thief — ruling 2

The player dealt combat damage mills cards only for the damage dealt by your Rogues, not for any other combat damage dealt to them at the same time.

Anowon, the Ruin Thief — ruling 3

You draw just one card, no matter how many creature cards the player mills beyond the first.

Anowon, the Ruin Thief — ruling 4

If Rogues you control deal combat damage to two players at once, Anowon’s ability triggers twice.

Anowon, the Ruin Thief : règles, fonctionnement et interactions (MTG)

Anowon, the Ruin Thief 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

Other Rogues you control get +1/+1. Whenever one or more Rogues you control deal combat damage to a player, that player mills a card for each 1 damage dealt to them. If the player mills at least one creature card this way, you draw a card. (To mill a card, a player puts the top card of their library into their graveyard.)

How it works : Anowon, the Ruin Thief

Original English text — Wizards of the Coast / Scryfall

#1September 25, 2020· Wizards of the Coast
Because damage remains marked on a creature until the damage is removed as the turn ends, nonlethal damage dealt to other Rogues you control may become lethal if Anowon leaves the battlefield during that turn.
No other card is named in this ruling.
#2September 25, 2020· Wizards of the Coast
The player dealt combat damage mills cards only for the damage dealt by your Rogues, not for any other combat damage dealt to them at the same time.
No other card is named in this ruling.
#3September 25, 2020· Wizards of the Coast
You draw just one card, no matter how many creature cards the player mills beyond the first.
No other card is named in this ruling.
#4September 25, 2020· Wizards of the Coast
If Rogues you control deal combat damage to two players at once, Anowon’s ability triggers twice.
No other card is named in this ruling.