Anthousa, Setessan Hero — ruling 1

If a land that hasn't been under your control continuously since your last turn began becomes a creature, it can't attack and its activated abilities that include {T} can't be activated. Notably, it can't be tapped for mana that turn.

Anthousa, Setessan Hero — ruling 2

Heroic abilities will resolve before the spell that caused them to trigger.

Anthousa, Setessan Hero — ruling 3

Heroic abilities will trigger only once per spell, even if that spell targets the creature with the heroic ability multiple times.

Anthousa, Setessan Hero — ruling 4

Heroic abilities won't trigger when a copy of a spell is created on the stack or when a spell's targets are changed to include a creature with a heroic ability.

Anthousa, Setessan Hero : règles, fonctionnement et interactions (MTG)

Anthousa, Setessan Hero 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

Heroic — Whenever you cast a spell that targets Anthousa, up to three target lands you control each become 2/2 Warrior creatures until end of turn. They're still lands.

How it works : Anthousa, Setessan Hero

Original English text — Wizards of the Coast / Scryfall

#1September 15, 2013· Wizards of the Coast
If a land that hasn't been under your control continuously since your last turn began becomes a creature, it can't attack and its activated abilities that include can't be activated. Notably, it can't be tapped for mana that turn.
No other card is named in this ruling.
#2September 15, 2013· Wizards of the Coast
Heroic abilities will resolve before the spell that caused them to trigger.
No other card is named in this ruling.
#3September 15, 2013· Wizards of the Coast
Heroic abilities will trigger only once per spell, even if that spell targets the creature with the heroic ability multiple times.
No other card is named in this ruling.
#4September 15, 2013· Wizards of the Coast
Heroic abilities won't trigger when a copy of a spell is created on the stack or when a spell's targets are changed to include a creature with a heroic ability.
No other card is named in this ruling.