Harbinger of Doom
For the most part, this campaign follows the published 4E rules as published by WotC, including errata. This now includes the “Essentials” line of materials, including Heroes of Shadow.
Immediate Interrupts on AOE or multiple targets
For immediate interrupts that interrupt attacks that include multiple targets, distance will be a consideration for when the interrupt occurs. Attacks that include targets closer than the interrupter will be resolved as normal. Attacks that include the interrupter, and those that occur on targets farther from the attacker, will be subject to any conditions of the interrupt.