FAQ is only tell about added more invaders. (https://querki.net/u/darker/spirit-island-faq/#!.bu6oeb6)
during ravage step,
ravage card is sand A,B.(both no defend.)
sand A with 1 town / sand B with 1 town, 1 explorer.
ravage action to sand A, add 1 blight, island card is flipped, blight card is 'a pall upon the land',
and i destroy 1 presence and remove 1 town on sand B, now sand B has only 1 explorer.
and i ravage action to sand B, damage is only 1(by explorer,)??