Hour of Devastation — ruling 1

There are many important moments in the story, but the most crucial—called “story spotlights”—are shown on cards. These cards have the Planeswalker symbol in their text box; this symbol has no effect on gameplay. You can read more about these events in the official Magic fiction at http://www.mtgstory.com.

Hour of Devastation — ruling 2

Creatures with indestructible that enter the battlefield after Hour of Devastation resolves will still have indestructible.

Hour of Devastation — ruling 3

Once Hour of Devastation begins to resolve, no player may take actions until it’s done. Notably, players can’t try to give a creature indestructible again to save it from the damage.

Hour of Devastation : règles, fonctionnement et interactions (MTG)

Hour of Devastation 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

All creatures lose indestructible until end of turn. Hour of Devastation deals 5 damage to each creature and each non-Bolas planeswalker.

How it works : Hour of Devastation

Original English text — Wizards of the Coast / Scryfall

#1January 19, 2018· Wizards of the Coast
There are many important moments in the story, but the most crucial—called “story spotlights”—are shown on cards. These cards have the Planeswalker symbol in their text box; this symbol has no effect on gameplay. You can read more about these events in the official Magic fiction at http://www.mtgstory.com.
No other card is named in this ruling.
#2July 14, 2017· Wizards of the Coast
Creatures with indestructible that enter the battlefield after Hour of Devastation resolves will still have indestructible.
No other card is named in this ruling.
#3July 14, 2017· Wizards of the Coast
Once Hour of Devastation begins to resolve, no player may take actions until it’s done. Notably, players can’t try to give a creature indestructible again to save it from the damage.
No other card is named in this ruling.