What happens when a regeneration shield is in effect?

A regeneration shield creates a specific effect that triggers when a permanent is destroyed. Instead of being destroyed, the regeneration shield replaces that destruction with the regeneration effect, allowing the permanent to remain on the battlefield. This means that when the regeneration shield is active, if the permanent would be destroyed, it instead becomes tapped and removed from combat, representing the alternate effect of regeneration.

When discussing the context of this effect, it's important to note that while a regeneration shield can protect a permanent from destruction, it does not prevent sacrificing or canceling any of the card's effects, nor does it impact a permanent's ability to attack again specifically. The unique aspect of regeneration is that it directly modifies the consequence of being destroyed rather than simply nullifying effects or allowing repeated attacks.