So, if I understand the lore of Glitch correctly, then we are part of the Giant's imaginations. Well, when the Rook attacks the Giants and invades their imaginations, shouldn't a part of the Rooks imagination leak into the Giants? This could manifest in the form of altering the trees and animals in the street being attacked into "Rook" versions of themselves, which can be cured using skills or items, or just take a while to return to normal after the Rook attack. Or, the Rook could send out his own agents during the attack, which scope out other streets. When the Rook gets low on health, he will teleport, or move, to the street his current agent is on with the least population of Glitch's.
Just throwing ideas out there which could add another dimension to the Rook attacks while fitting in with the lore of this amazing game.