Trial of Solidarity

When this enchantment enters, creatures you control get +2/+1 and gain vigilance until end of turn.
When a Cartouche you control enters, return this enchantment to its owner's hand.

Amonkhet Remastered

When Trial of Solidarity enters the battlefield, creatures you control get +2/+1 and gain vigilance until end of turn.
When a Cartouche enters the battlefield under your control, return Trial of Solidarity to its owner's hand.

"You will succeed as one or fail as many."

Amonkhet

Each Trial has an ability to return to your hand when a Cartouche enters the battlefield under your control. The Trial is returned to its owner’s hand only if it’s on the battlefield as the ability resolves.

If an effect allows you to exert a creature as it attacks, you may do so even if it has vigilance. It won’t be tapped.

Trial of Solidarity’s triggered ability affects only creatures you control at the time it resolves. It won’t affect creatures that come under your control later in the turn.