Interruptive Action

Interruptive Actions are taken in response to a specific trigger, and can be used to interrupt another creature's action. This is different from an Opportunity Action, which can only be taken when a creature is granted an Opportunity. When an Interruptive Action is triggered, your action occurs immediately, interrupting the triggering action. This may disrupt the triggering creature’s action or changes its effects.

You are limited to taking only one Interruptive or Reactive action per round. You may only use a single action in response to a triggering event (i.e. if you had two powers with a similar trigger, you would have to choose which power to utilize, even if they were different action types). You may not use Interruptive or Reactive actions during your turn.

Example
Ariana is suffering ongoing Fire damage, and is using the Recovery ability to make a Saving Throw. Just as she makes the Saving Throw, her ally Fagan uses the Suppress orison to give her a bonus to her Saving Throw.