make void the counsel - defeat their plans for repelling the enemy (2Ch 32:1-4; Isa 19:3; Isa 22:9, Isa 22:11). Or their schemes of getting help by having recourse to idols [Calvin].
in this place - The valley of Hinnom was to be the place of the Chaldean encampment; the very place where they looked for help from idols was to be the scene of their own slaughter.