Hall of Storm Giants — ruling 1

If Hall of Storm Giants enters the battlefield at the same time as one or more other lands, it doesn't take those lands into consideration when determining how many other lands you control.

Hall of Storm Giants — ruling 2

If you turn Hall of Storm Giants into a creature but haven't controlled it continuously since your most recent turn began, you won't be able to activate its mana ability or attack with it.

Hall of Storm Giants — ruling 3

If you activate Hall of Storm Giants's last ability multiple times, it gains multiple instances of ward {3}. Each of those instances will trigger separately and ask the opponent who controls the spell or ability to pay {3}. If they don't for any of those instances, the spell or ability will be countered.

Hall of Storm Giants — ruling 4

If an opponent casts a spell or ability that targets Hall of Storm Giants, and you activate the last ability in response, the ward ability Hall of Storm Giants gains won't trigger. (However, if it already had ward at the moment it became the target of the spell or ability, that instance of ward would trigger.)

Hall of Storm Giants : règles, fonctionnement et interactions (MTG)

Hall of Storm Giants 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

If you control two or more other lands, this land enters tapped. : Add . : Until end of turn, this land becomes a 7/7 blue Giant creature with ward . It's still a land. (Whenever it becomes the target of a spell or ability an opponent controls, counter it unless that player pays .)

How it works : Hall of Storm Giants

Original English text — Wizards of the Coast / Scryfall

#1July 23, 2021· Wizards of the Coast
If Hall of Storm Giants enters the battlefield at the same time as one or more other lands, it doesn't take those lands into consideration when determining how many other lands you control.
No other card is named in this ruling.
#2July 23, 2021· Wizards of the Coast
If you turn Hall of Storm Giants into a creature but haven't controlled it continuously since your most recent turn began, you won't be able to activate its mana ability or attack with it.
No other card is named in this ruling.
#3July 23, 2021· Wizards of the Coast
If you activate Hall of Storm Giants's last ability multiple times, it gains multiple instances of ward . Each of those instances will trigger separately and ask the opponent who controls the spell or ability to pay . If they don't for any of those instances, the spell or ability will be countered.
No other card is named in this ruling.
#4July 23, 2021· Wizards of the Coast
If an opponent casts a spell or ability that targets Hall of Storm Giants, and you activate the last ability in response, the ward ability Hall of Storm Giants gains won't trigger. (However, if it already had ward at the moment it became the target of the spell or ability, that instance of ward would trigger.)
No other card is named in this ruling.