Wail of the Sacrificed is an ability for the Advent Rebel's Temple of Communion that allows it to sacrifice a planet's population to deal damage to all ships and structures in adjacent gravity wells. Make sure that your fleet or at least the fragile part of it is not at adjacent planets from the source or they will be destroyed with the enemy. TEC: Novalith the planet... with lower population count the damage goes down as well. Or suicide a few Krosovs. Vasari: Use Kostura and jump in right on the dangerous planet.... quite easy. Just watch out for possible overlapping wail.