The legend Ivern has an effect 'it can be swapped back when scored'. What does this mean?

The text "It can be swapped back when scored" on the Brush battlefield token (created by the Green Father Legend) refers to a specific interaction involving the Replace game mechanic.

When you use the Green Father's ability, you replace a battlefield with a Brush token. Per the official rules and clarifications, here is how the "swap back" mechanic works:

• Replacing: When you create the Brush token, it replaces the original battlefield. The token inherits all statuses and conditions that were on the original battlefield at that time (Rule 438.1).
• Swapping Back: When you score at the location of the Brush token, you have the option to trigger its ability to "swap back."
• The Result: When you swap back, the Brush token ceases to exist. The original card that it replaced is returned to the battlefield space. Because the original battlefield was "replaced" rather than destroyed or removed, it returns inheriting any current effects and statuses it had previously (Rule 438.7.b).

Essentially, this ability allows you to temporarily alter a battlefield to benefit your specific unit types (Bird, Cat, Dog, Poro, and Ivern) and then revert it to its original form once you have scored there.

According to the Rules FAQ Clarification (2026-04-29): "The Brush token will cease to exist. When swapping back, a player can choose to swap back to any object that was replaced, including the original battlefield."